14273 receptor, a novel G-protein coupled receptor

ABSTRACT

The present invention relates to a newly identified receptor belonging to the superfamily of G-protein-coupled receptors. The invention also relates to polynucleotides encoding the receptor. The invention further relates to methods using the receptor polypeptides and polynucleotides as a target for diagnosis and treatment in receptor-mediated disorders, specifically, cardiovascular diseases, including congestive heart failure. The invention further relates to drug-screening methods using the receptor polypeptides and polynucleotides to identify agonists and antagonists for diagnosis and treatment. The invention further encompasses agonists and antagonists based on the receptor polypeptides and polynucleotides. The invention further relates to procedures for producing the receptor polypeptides and polynucleotides.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/171,027, filed Jun. 12, 2002, now abandoned, which is a divisionalapplication of U.S. patent application Ser. No. 09/456,455, filed Dec.8, 1999, now U.S. Pat. No. 6,448,005, which is a continuation-in-partapplication of U.S. patent application Ser. No. 09/261,599, filed Feb.26, 1999, now U.S. Pat. No. 6,395,877, which is a continuation-in-partof U.S. patent application Ser. No. 09/223,538, filed Dec. 30, 1998, nowabandoned, which is a continuation-in-part of U.S. patent applicationSer. No. 09/107,761, filed Jun. 30, 1998, now abandoned, which arehereby incorporated herein in their entirety by reference.

FIELD OF THE INVENTION

The present invention relates to a newly identified receptor belongingto the superfamily of G-protein-coupled receptors. The invention alsorelates to polynucleotides encoding the receptor. The invention furtherrelates to methods using the receptor polypeptides and polynucleotidesas a target for diagnosis and treatment in receptor-mediated disorders,specifically, cardiovascular diseases, including congestive heartfailure. The invention further relates to drug-screening methods usingthe receptor polypeptides and polynucleotides to identify agonists andantagonists for diagnosis and treatment. The invention furtherencompasses agonists and antagonists based on the receptor polypeptidesand polynucleotides. The invention further relates to procedures forproducing the receptor polypeptides and polynucleotides.

BACKGROUND OF THE INVENTION

G-Protein Coupled Receptors

G-protein coupled receptors (GPCRs) constitute a major class of proteinsresponsible for transducing a signal within a cell. GPCRs have threestructural domains: an amino terminal extracellular domain, atransmembrane domain containing seven transmembrane segments, threeextracellular loops, and three intracellular loops, and a carboxyterminal intracellular domain. Upon binding of a ligand to anextracellular portion of a GPCR, a signal is transduced within the cellthat results in a change in a biological or physiological property ofthe cell. GPCRs, along with G-proteins and effectors (intracellularenzymes and channels modulated by G-proteins), are the components of amodular signaling system that connects the state of intracellular secondmessengers to extracellular inputs.

GPCR genes and gene-products are potential causative agents of disease(Spiegel et al., J. Clin. Invest. 92:1119-1125 (1993); McKusick et al.,J. Med. Genet. 30:1-26 (1993)). Specific defects in the rhodopsin geneand the V2 vasopressin receptor gene have been shown to cause variousforms of retinitis pigmentosum (Nathans et al., Annu. Rev. Genet.26:403-424(1992)), and nephrogenic diabetes insipidus (Holtzman et al.,Hum. Mol. Genet. 2:1201-1204 (1993)). These receptors are of criticalimportance to both the central nervous system and peripheralphysiological processes. Evolutionary analyses suggest that the ancestorof these proteins originally developed in concert with complex bodyplans and nervous systems.

The GPCR protein superfamily can be divided into five families: FamilyI, receptors typified by rhodopsin and the β2-adrenergic receptor andcurrently represented by over 200 unique members (Dohlman et al., Annu.Rev. Biochem. 60:653-688 (1991)); Family II, the parathyroidhormone/calcitonin/secretin receptor family (Juppner et al., Science254:1024-1026 (1991); Lin et al., Science 254:1022-1024 (1991)); FamilyIII, the metabotropic glutamate receptor family (Nakanishi, Science 258597:603 (1992)); Family IV, the cAMP receptor family, important in thechemotaxis and development of D. discoideum (Klein et al., Science241:1467-1472 (1988)); and Family V, the fungal mating pheromonereceptors such as STE2 (Kurjan, Annu. Rev. Biochem. 61:1097-1129(1992)).

There are also a small number of other proteins which present sevenputative hydrophobic segments and appear to be unrelated to GPCRs; theyhave not been shown to couple to G-proteins. Drosophila expresses aphotoreceptor-specific protein, bride of sevenless (boss), aseven-transmembrane-segment protein which has been extensively studiedand does not show evidence of being a GPCR (Hart et al., Proc. Natl.Acad. Sci. USA 90:5047-5051 (1993)). The gene frizzled (fz) inDrosophila is also thought to be a protein with seven transmembranesegments. Like boss, fz has not been shown to couple to G-proteins(Vinson et al., Nature 338:263-264 (1989)).

G proteins represent a family of heterotrimeric proteins composed of α,β and γ subunits, that bind guanine nucleotides. These proteins areusually linked to cell surface receptors, e.g., receptors containingseven transmembrane segments. Following ligand binding to the GPCR, aconformational change is transmitted to the G protein, which causes theα-subunit to exchange a bound GDP molecule for a GTP molecule and todissociate from the βγ-subunits. The GTP-bound form of the α-subunittypically functions as an effector-modulating moiety, leading to theproduction of second messengers, such as cAMP (e.g., by activation ofadenyl cyclase), diacylglycerol or inositol phosphates. Greater than 20different types of α-subunits are known in humans. These subunitsassociate with a smaller pool of β and γ subunits. Examples of mammalianG proteins include Gi, Go, Gq, Gs and Gt. G proteins are describedextensively in Lodish et al., Molecular Cell Biology, (ScientificAmerican Books Inc., New York, N.Y., 1995), the contents of which areincorporated herein by reference. GPCRs, G proteins and G protein-linkedeffector and second messenger systems have been reviewed in TheG-Protein Linked Receptor Fact Book, Watson et al., eds., Academic Press(1994).

GPCRs are a major target for drug action and development. Accordingly,it is valuable to the field of pharmaceutical development to identifyand characterize previously unknown GPCRs. The present inventionadvances the state of the art by providing a previously unidentifiedhuman GPCR.

SUMMARY OF THE INVENTION

It is an object of the invention to identify novel GPCRs.

It is a further object of the invention to provide novel GPCRpolypeptides that are useful as reagents or targets in receptor assaysapplicable to treatment and diagnosis of GPCR-mediated disorders.

It is a further object of the invention to provide polynucleotidescorresponding to the novel GPCR receptor polypeptides that are useful astargets and reagents in receptor assays applicable to treatment anddiagnosis of GPCR-mediated disorders and useful for producing novelreceptor polypeptides by recombinant methods.

A specific object of the invention is to identify compounds that act asagonists and antagonists and modulate the expression of the novelreceptor.

A further specific object of the invention is to provide compounds thatmodulate expression of the receptor for treatment and diagnosis ofGPCR-related disorders.

The invention is thus based on the identification of a novel GPCR,designated the 14273 receptor.

The invention provides isolated 14273 receptor polypeptides including apolypeptide having the amino acid sequence shown in SEQ ID NO:1 (human)and SEQ ID NO:4 (murine), or the amino acid sequence encoded by the cDNAdeposited as ATCC No. PTA-1143 (“the deposited cDNA”).

The invention also provides isolated 14273 receptor nucleic acidmolecules having the sequence shown in SEQ ID NO:2 (human) and SEQ IDNO:5 (murine) or in the deposited cDNA.

The invention also provides variant polypeptides having an amino acidsequence that is substantially homologous to the amino acid sequenceshown in SEQ ID NO: 1 or SEQ ID NO:4 or encoded by the deposited cDNA.

The invention also provides variant nucleic acid sequences that aresubstantially homologous to the nucleotide sequence shown in SEQ ID NO:2or SEQ ID NO:5 or in the deposited cDNA.

The invention also provides fragments of the polypeptide shown in SEQ IDNO:1 or SEQ ID NO:4 and nucleotide shown in SEQ ID NO:2 or SEQ ID NO:5,as well as substantantially homologous fragments of the polypeptide ornucleic acid.

The inventors have linked expression of the receptor polynucleotides tocardiovascular disease and specifically to congestive heart failure. Theinventors have found that receptor mRNA is induced in hypertrophic humancardiac myocytes and that expression correlates with morphologicalchange. This induction is observed in ischemic and dilated hearts.

Therefore, the invention also provides receptor variants that correlatewith the cardiovascular disorders.

Cardiac hypertrophy is the principal response of the heart to overloadfrom any cause including ischemia/reperfusion injury, myocardialinfarction, longstanding heart failure, vascular wall remodeling,ventricular remodeling, dilated cardiomyopathy, rapid ventricularpacing, coronary microembolism, pressure-overload, aortic banding,coronary artery ligation, end stage heart failure, tachyarrhythmia,bradyarrhythmia, valvar heart disease, and hypertension. Hypertrophy isa strong, independent predictor of cardiovascular death and isassociated with diastolic dysfunction. Since adult cardiac myocytes areterminally differentiated cells, the increase in muscle mass seen incardiac hypertrophy occurs predominantly by an increase in myocyte size.At the cellular level, the events leading to cardiac hypertrophy havebeen divided into (1) extracellular hypertrophic stimulus; (2)intracellular signal transduction; and (3) activation of nuclear eventsthat allow for the hypertrophic phenotype.

Further experiments by the inventors have shown that in transgenic mousemodels in which the novel receptor is overexpressed, the induction ofcardiac hypertrophy is observed. Histological examination of heartsderived from these transgenic mice shows a significant increase in theheart:body weight ratio. In several independent sets of transgenicanimals, enlargement of the heart and heart failure is a significantoutcome. Observations include enlarged cardiomyocytes, biventriculardilatation, atrial thrombi, and interstitial fibrosis.

Additional experiments have shown that the 14273 receptor wasupregulated in a rat pressure overload model. A rat pressure overloadmodel was generated by placing a constrictive band around the aorta toinduce a state of cardiac hypertrophy (Kimura et al. Am. J. Physiol.256:H1006-H1011 (1989)). The 14273 receptor was shown to be induced atthe mRNA level following banding of the aorta. This increase inexpression was correlated with the hypertrophic phenotype. Results wereobtained by in situ hybridization.

Additional experiments showed that in transgenic mice overexpressing the14273 receptor, that receptor mRNA and protein levels were correlatedwith the severity of the phenotype. The phenotype seen in the 14273transgenic animals ranged from severe, with death by 3-4 weeks, to mild,showing only subtle pathohistological findings, as evidenced by stainingcardiac myocytes from wild-type and transgenic animals with wheat germagglutinin or Masson's Trichrome. The wheat germ agglutinin outlinesmyocytes, which in turn allows the determination of the degree ofhypertrophy, while the Trichrome identifies collagen fibers in tissuesections. Collagen fibers are a hallmark of fibrosis. The severity ofthe phenotype was correlated with increased transgene expression at boththe mRNA and protein levels. Severity of the phenotype was proportionalto the level of 14273 receptor expression observed. In these experimentshypertrophy was observed in both the nucleus and cytoplasm of thehypertrophic myocytes. In addition, histological results from theseanimals showed myocyte disorganization, as well as atrial andventricular loss. This was then associated with subsequent interstitialfibrosis as a result of the replacement of dead myocytes with connectivetissue. Fibroelastosis (deficiency in elastic fiber) was also observed.This is evidence of a loss of general elastic tone from cardiac tissue.Finally, atrial thrombosis was observed to result from the abovepathological series of events. In addition, along with increasedexpression of the 14273 receptor, the inventors observed coordinateincreased expression of atrial natriuretic factor (ANF). This factor, anatural diuretic, is produced in increased amounts during cardiachypertrophy and, accordingly, serves as a marker of cardiac hypertrophy.

The invention also provides vectors and host cells for expressing thereceptor nucleic acid molecules and polypeptides and particularlyrecombinant vectors and host cells. The invention particularly provideshost cells that provide a model for cardiovascular diseases bycontaining specific variants that are correlated with the disorders.

The invention also provides methods of making the vectors and host cellsand methods for using them to produce the receptor nucleic acidmolecules and polypeptides.

The invention also provides antibodies that selectively bind thereceptor polypeptides and fragments.

The invention also provides methods of screening for compounds thatmodulate the activity of the receptor polypeptides. Modulation can be atthe level of the polypeptide receptor or at the level of controlling theexpression of nucleic acid (RNA or DNA) expressing the receptorpolypeptide.

The invention also provides a process for modulating receptorpolypeptide activity, especially using the screened compounds, includingto treat conditions related to expression of the receptor polypeptides.

Since the receptor polynucleotides have been linked to cardiovasculardiseases, the invention provides methods for modulating receptorpolypeptide and nucleic acid expression in subjects having, orpredisposed to having, cardiovascular diseases, cells from thesesubjects, and model systems for the disorders.

The invention also provides diagnostic assays for determining thepresence of and level of the receptor polypeptides or nucleic acidmolecules in a biological sample.

The invention also provides diagnostic assays for determining thepresence of a mutation in the receptor polypeptides or nucleic acidmolecules.

Since the receptor polynucleotides have been linked to cardiovasculardiseases, the invention provides diagnostic assays for determining thepresence, level, or mutation of receptor polynucleotides andpolypeptides preferably in subjects with, or having a predisposition to,cardiovascular diseases, cells from these subjects, and model systemsfor the disorders.

DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C show the human 14273 nucleotide sequence (SEQ ID NO:2) andthe deduced 14273 amino acid sequence (SEQ ID NO:1). It is predictedthat amino acids 1-45 of SEQ ID NO:1 constitute the amino terminalextracellular domain, amino acids 46-321 constitute the region spanningthe transmembrane domain, and amino acids 322-361 of SEQ ID NO:1constitute the carboxy terminal intracellular domain. The transmembranedomain contains seven transmembrane segments, three extracellular loopsand three intracellular loops. The transmembrane segments are found fromabout amino acid 46 to about amino acid 66, from about amino acid 75 toabout amino acid 98, from about amino acid 113 to about amino acid 134,from about amino acid 156 to about amino acid 177, from about amino acid209 to about amino acid 227, from about amino acid 266 to about aminoacid 289, and from about amino acid 297 to about amino acid 321 of SEQID NO:1. Within the region spanning the entire transmembrane domain arethree intracellular and three extracellular loops. The threeintracellular loops are found from about amino acid 67 to about aminoacid 74, from about amino acid 135 to about amino acid 155, and fromabout amino acid 228 to about amino acid 265 of SEQ ID NO:1. The threeextracellular loops are found at from about amino acid 99 to about aminoacid 112, from about amino acid 178 to about amino acid 208, and fromabout amino acid 290 to about amino acid 296 of SEQ ID NO:1.

The transmembrane domain includes a sequence, ERM, corresponding to theGPCR signal transduction signature, DRY, at residues 135-137 of SEQ IDNO:1. The sequence includes an arginine at residue 136 of SEQ ID NO:1,an invariant amino acid in GPCRs.

FIG. 2 shows a comparison of the human 14273 receptor against theProsite data base of protein patterns, specifically showing a high scoreagainst the seven transmembrane segment rhodopsin superfamily (SEQ IDNO:3). The underlined area shows a sequence corresponding to the GPCRsignature, and specifically the position of an arginine residue,conserved in GPCRs. The most commonly conserved sequence is anaspartate, arginine, tyrosine (DRY) triplet. DRY is implicated in signaltransduction. Arginine is invariant. Aspartate is conservatively placedin several GPCRs. In the present case, the arginine is found in thesequence ERM, which matches the position of DRY or invariant arginine inGPCRs of the rhodopsin superfamily of receptors.

FIG. 3 shows an analysis of the human 14273 amino acid sequence: αβturnand coil regions; hydrophilicity; amphipathic regions; flexible regions;antigenic index; and surface probability plot.

FIG. 4 shows a human 14273 receptor hydrophobicity plot, showing theseven transmembrane segments. (FIh14237: SEQ ID NO: 1)

FIG. 5 shows an analysis of the human 14273 open reading frame for aminoacids corresponding to specific functional sites. Glycosylation sitesare found from about amino acids 21-24 and 322-325 of SEQ ID NO:1. Acyclic AMP- and cyclic GMP-dependent protein kinase phosphorylation siteis found at about amino acids 239-242 of SEQ ID NO:1. A protein kinase Cphosphorylation site is found from about amino acids 237-239 and 350-352of SEQ ID NO:1. A casein kinase II phosphorylation site is found fromabout amino acids 256-259 of SEQ ID NO:1. N-myristoylation sites arefound from about amino acids 57-62, 72-77, and 343-348 of SEQ ID NO:1.(SEQ ID NO: 6, SEQ ID NO: 7, and SEQ ID NO: 8, respectively). Anamidation site is found at about amino acids 150-153 of SEQ ID NO:1. Aleucine zipper pattern is shown at about amino acids 106-127 of SEQ IDNO:1(SEQ ID NO:9). In addition, amino acids corresponding in position tothe GPCR signature and containing the invariant arginine are found inthe sequence ERM at amino acids 135-137 of SEQ ID NO:1.

FIG. 6 shows human 14273 receptor transmembrane segments predicted byMemsat (A) Predicted segments for the presumed unprocessed peptide (B)Transmembrane segments for the presumed mature peptide. Numbering forthe presumed mature peptide has been adjusted for the removal of thefirst 36 amino acids. (FIh14237: SEQ ID NO: 1; FIh14273 mature; aninoacids 37-361 of SEQ ID NO:1)

FIGS. 7A-7B show the murine ortholog of 14273 nucleotide sequence (SEQID NO:5) and the deduced 14273 amino acid sequence (SEQ ID NO:4). It ispredicted that amino acids 1-45 of SEQ ID NO:4 constitute the aminoterminal extracellular domain, amino acids 46-321 of SEQ ID NO:4constitute the region spanning the transmembrane domain, and amino acids322-361 of SEQ ID NO:4 constitute the carboxy terminal intracellulardomain. The transmembrane domain contains seven transmembrane segments,three extracellular loops and three intracellular loops. Thetransmembrane segments are found from about amino acid 96 to about aminoacid 66, from about amino acid 77 to about amino acid 98, from aboutamino acid 113 to about amino acid 134, from about amino acid 156 toabout amino acid 177, from about amino acid 209 to about amino acid 227,from about amino acid 266 to about amino acid 289, and from about aminoacid 297 to about amino acid 321 of SEQ ID NO:4. Within the regionspanning the entire transmembrane domain are three intracellular andthree extracellular loops. The three intracellular loops are found fromabout amino acid 67 to about amino acid 76, from about amino acid 135 toabout amino acid 155, and from about amino acid 228 to about amino acid265 of SEQ ID NO:4. The three extracellular loops are found at fromabout amino acid 99 to about amino acid 112, from about amino acid 178to about amino acid 208, and from about amino acid 290 to about aminoacid 296 of SEQ ID NO:4.

The transmembrane domain includes a sequence, ERM, corresponding to theGPCR signal transduction signature, DRY, at residues 135-137 of SEQ IDNO:4. The sequence includes an arginine at residue 136 of SEQ ID NO:4,an invariant amino acid in GPCRs.

FIG. 8 shows a comparison of the murine 14273 receptor against theProsite data base of protein patterns, specifically showing a high scoreagainst the seven transmembrane segment rhodopsin superfamily (SEQ IDNO:3). The underlined area shows a sequence corresponding to the GPCRsignature, and specifically the position of an arginine residue,conserved in GPCRs. The most commonly conserved sequence is anaspartate, arginine, tyrosine (DRY) triplet. DRY is implicated in signaltransduction. Arginine is invariant. Aspartate is conservatively placedin several GPCRs. In the present case, the arginine is found in thesequence ERM, which matches the position of DRY or invariant arginine inGPCRs of the rhodopsin superfamily of receptors.

FIG. 9 shows an analysis of the murine 14273 amino acid sequence: αβturnand coil regions; hydrophilicity; amphipathic regions; flexible regions;antigenic index; and surface probability plot.

FIG. 10 shows a murine 14273 receptor hydrophobicity plot, showing theseven transmembrane segments. (14273m: SEQ ID NO:4)

FIG. 11 shows an analysis of the murine 14273 open reading frame foramino acids corresponding to specific functional sites. Glycosylationsites are found from about amino acids 21-24 and 322-325 of SEQ ID NO:4.A cyclic AMP- and cyclic GMP-dependent protein kinase phosphorylationsite is found at about amino acids 239-242 of SEQ ID NO:4. A proteinkinase C phosphorylation site is found from about amino acids 237-239and 350-352 of SEQ ID NO:4. Casein kinase II phosphorylation sites arefound from about amino acids 40-43 and 256-259 of SEQ ID NO:4.N-myristoylation sites are found from about amino acids 57-62, 72-77,and 343-348 of SEQ ID NO:4. An amidation site is found at about aminoacids 150-153 of SEQ ID NO:4. A leucine zipper pattern is shown at aboutamino acids 106-127 of SEQ ID NO:4. In addition, amino acidscorresponding in position to the GPCR signature and containing theinvariant arginine are found in the sequence ERM at amino acids 135-137of SEQ ID NO:4. A glycosaminoglycan attachment site is found at aboutamino acids 148-151 of SEQ ID NO:4.

FIG. 12 shows murine 14273 receptor transmembrane segments predicted byMemsat (A) predicted segments for the presumed unprocessed peptide (b)transmembrane segment for the presumed mature peptide. Numbering for thepresumed mature peptide has been adjusted for the removal of the first36 amino acids.

DETAILED DESCRIPTION OF THE INVENTION

Receptor Function/Signal Pathway

The 14273 receptor protein is a GPCR that participates in signalingpathways. As used herein, a “signaling pathway” refers to the modulation(e.g., stimulation or inhibition) of a cellular function/activity uponthe binding of a ligand to the GPCR (14273 protein). Examples of suchfunctions include mobilization of intracellular molecules thatparticipate in a signal transduction pathway, e.g., phosphatidylinositol4,5-bisphosphate (PIP₂), inositol 1,4,5-triphosphate (IP₃) and adenylatecyclase; polarization of the plasma membrane; production or secretion ofmolecules; alteration in the structure of a cellular component; cellproliferation, e.g., synthesis of DNA; cell migration; celldifferentiation; and cell survival. Since the 14273 receptor protein isexpressed in brain, heart, skeletal muscle, thymus, prostate, uterus andplacenta, cells participating in a 14273 receptor protein signalingpathway include, but are not limited to, cells derived from thesetissues.

The response mediated by the receptor protein depends on the type ofcell. For example, in some cells, binding of a ligand to the receptorprotein may stimulate an activity such as release of compounds, gatingof a channel, cellular adhesion, migration, differentiation, etc.,through phosphatidylinositol or cyclic AMP metabolism and turnover whilein other cells, the binding of the ligand will produce a differentresult. Regardless of the cellular activity/response modulated by thereceptor protein, it is universal that the protein is a GPCR andinteracts with G proteins to produce one or more secondary signals, in avariety of intracellular signal transduction pathways, e.g., throughphosphatidylinositol or cyclic AMP metabolism and turnover, in a cell.

As used herein, “phosphatidylinositol turnover and metabolism” refers tothe molecules involved in the turnover and metabolism ofphosphatidylinositol 4,5-bisphosphate (PIP₂) as well as to theactivities of these molecules. PIP₂ is a phospholipid found in thecytosolic leaflet of the plasma membrane. Binding of ligand to thereceptor activates, in some cells, the plasma-membrane enzymephospholipase C that in turn can hydrolyze PIP₂ to produce1,2-diacylglycerol (DAG) and inositol 1,4,5-triphosphate (IP₃). Onceformed IP₃ can diffuse to the endoplasmic reticulum surface where it canbind an IP₃ receptor, e.g., a calcium channel protein containing an IP₃binding site. IP₃ binding can induce opening of the channel, allowingcalcium ions to be released into the cytoplasm. IP₃ can also bephosphorylated by a specific kinase to form inositol1,3,4,5-tetraphosphate (IP₄), a molecule which can cause calcium entryinto the cytoplasm from the extracellular medium. IP₃ and IP₄ cansubsequently be hydrolyzed very rapidly to the inactive productsinositol 1,4-biphosphate (IP₂) and inositol 1,3,4-triphosphate,respectively. These inactive products can be recycled by the cell tosynthesize PIP₂. The other second messenger produced by the hydrolysisof PIP₂, namely 1,2-diacylglycerol (DAG), remains in the cell membranewhere it can serve to activate the enzyme protein kinase C. Proteinkinase C is usually found soluble in the cytoplasm of the cell, but uponan increase in the intracellular calcium concentration, this enzyme canmove to the plasma membrane where it can be activated by DAG. Theactivation of protein kinase C in different cells results in variouscellular responses such as the phosphorylation of glycogen synthase, orthe phosphorylation of various transcription factors, e.g., NF-kB. Thelanguage “phosphatidylinositol activity”, as used herein, refers to anactivity of PIP₂ or one of its metabolites.

Another signaling pathway in which the receptor may participate is thecAMP turnover pathway. As used herein, “cyclic AMP turnover andmetabolism” refers to the molecules involved in the turnover andmetabolism of cyclic AMP (cAMP) as well as to the activities of thesemolecules. Cyclic AMP is a second messenger produced in response toligand-induced stimulation of certain G protein coupled receptors. Inthe cAMP signaling pathway, binding of a ligand to a GPCR can lead tothe activation of the enzyme adenyl cyclase, which catalyzes thesynthesis of cAMP. The newly synthesized cAMP can in turn activate acAMP-dependent protein kinase. This activated kinase can phosphorylate avoltage-gated potassium channel protein, or an associated protein, andlead to the inability of the potassium channel to open during an actionpotential. The inability of the potassium channel to open results in adecrease in the outward flow of potassium, which normally repolarizesthe membrane of a neuron, leading to prolonged membrane depolarization.

Polypeptides

The invention is based on the discovery of a novel G-coupled proteinreceptor. Specifically, an expressed sequence tag (EST) was selectedbased on homology to G-protein-coupled receptor sequences. This EST wasused to design primers based on sequences that it contains and used toidentify a cDNA from a human fetal brain cDNA library. Positive cloneswere sequenced and the overlapping fragments were assembled. Analysis ofthe assembled sequence revealed that the cloned cDNA molecule encodes aG-protein coupled receptor. The amino acid sequence of this receptorshows homology with galanin receptors, chemokine receptors andsomatostatin.

Galanin is a small neuroendocrine peptide with 29 amino acids. The majorbiological functions are to promote growth hormone release, inhibitglucose-induced insulin release, impair cognitive function, stimulatefeeding behavior, and regulate motility in the gastrointestinal tract.For background and functions of galanin see U.S. Pat. No. 5,756,460.See, also, WO 98/15570 for teaching regarding galanin and galaninreceptor function. These documents are herein incorporated by referencefor these teachings.

RH linkage analysis was performed using the Map Manager QTb 23 softwarepackage. The 14273 receptor was found to map to human chromosome 10,10.0 cR3000 telomeric to the Whitehead Institute framework markerD10S583, and 13.3 cR3000 centromeric of the Whitehead framework markerD10S185. Two point LOD scores for linkage were 15.5 for D10S583 and 14.4for D10S185. This region corresponds to a cytogenetic location of10q23.1-23.3. This location places it in close proximity to the regiondefined as CMD1C, cardiomyopathy, dilated, 1C. Bowles, K. R., et al. (J.Clin. Invest. 98:1344-1360 (1996)) reported the discovery of the thirdlocus for a pure autosomal dominant familial dilated cardiomyopathy onchromosome 10q21-q23. In addition to the familial dilatedcardiomyopathy, the family studied in this report had associated mitralvalve prolapse and mitral regurgitation. It has been demonstrated(Sanyal et al., Pediatrics 63:116-122 (1979)) that these result fromdegeneration of the posterior papillary muscles or ventricularmyocardium in patients, causing instability of the mitral apparatus andsecondary prolapse. Since familial dilated cardiomyopathy is a primarydisorder of the ventricular myocardium due to a genetically-determinedprotein defect (such as a cytoskeletal protein), which would alsoinvolve the papillary muscles, the dilated cardiomyopathy-causingprotein defect could also be the underlying cause of the associatedmitral valve prolapse.

Dilated cardiomyopathy is the most common form of cardiomyopathy. Manycauses have been described but most commonly the disease is consideredidiopathic. Patients generally present signs and symptoms of congestiveheart failure. Diagnosis generally depends on evidence of ventriculardilatation and dysfunction. Premature death, especially cardiac deathfrom ventricular arrhythmias or ischemia is common. In a significantnumber of cases, a familial inheritance pattern is observed withautosomal dominant transmission being the most common form oftransmission. The underlying genetic defect was not known. As discussedabove, a form of familial dilated cardiomyopathy was mapped to the longarm of chromosome 10 (10q21-10q23) in one family in which the phenotypewas a pure dilated cardiomyopathy with mitral valve prolapse (citeabove).

In mapping the 14273 receptor to a specific genetic locationcorresponding to 10q23.1-23.3, the inventors have correlated thereceptor that is the subject of the invention to the region defined ascardiomyopathy dilated 1C. This provides the first association of aspecific gene with this locus, providing the basis for a genetic lesionassociated with dilated cardiomyopathy.

The expression of the 14273 receptor is induced at the RNA level inhypertrophic cardiac myocytes in diseased human hearts. This includes,but is not limited to, both dilated and ischemic hearts. In addition,transgenic mice overexpressing the 14273 receptor developedcardiomyocyte hypertrophy, many of these mice dying from heart failure.In several independently constructed series of transgenic animals inwhich the 14273 receptor can be specifically overexpressed incardiomyocytes, heart histopathology shows biventricular dilatation,cardiomyocyte hypertrophy, atrial thrombi, and interstitial fibrosis. Asignificant number of affected mice show a heart:body weight ratiosignificantly increased. In transgenic mice in which the receptor isexpressed and in which the hypertrophic phenotype is developed, receptormRNA and protein levels can be correlated with the severity of thephenotype. In one series, the ratios are approximately 1.5-2.7.Enlargement of atrium, ventricle thrombosis in the atrium, edema in thechest, and breathing difficulties, were observed. In a pressure overloadmodel (rat), cardiac hypertrophy was induced by banding of the aorta.Development of the hypertrophic phenotype was correlated with inductionof the 14273 receptor at the mRNA level by 22 weeks after banding.Accordingly, the inventors have discovered a novel gene that can producecardiovascular disease as well as serve as a target for treatment anddiagnosis.

The invention thus relates to a novel GPCR having the deduced amino acidsequence shown in FIG. 1 (SEQ ID NO:1) or having the amino acid sequenceencoded by the deposited cDNA, ATCC No. PTA-1143. The invention alsorelates to the mouse ortholog corresponding to the novel human GPCRhaving the deduced amino acid sequence shown in FIG. 7 (SEQ ID NO:4) orhaving the amino acid sequence encoded by the deposited cDNA, ATCC No.PTA-1143.

The deposit will be maintained under the terms of the Budapest Treaty onthe International Recognition of the Deposit of Microorganisms. Thedeposit is provided as a convenience to those of skill in the art and isnot an admission that a deposit is required under 35 U.S.C. § 112. Thedeposited sequence, as well as the polypeptide encoded by the sequence,is incorporated herein by reference and controls in the event of anyconflict, such as a sequencing error, with description in thisapplication.

Much of the detailed description is directed specifically to the humanreceptor polypeptide or nucleic acid. However, it is understood thatthis description applies also to the murine ortholog with the provisothat specific regions, such as segments, domains, fragments, antigenicsites, and the like, would be modified according to the sequence detailsand domain analysis provided for the mouse ortholog in the figuresherein. Accordingly, where the description refers to the 14273 receptorgenerically, this description refers to both the murine and humanreceptor. Where the description would necessarily be limited to thehuman receptor (as for example, in designating specific fragments,segments, or domains), to ascertain the corresponding details pertainingto the murine ortholog, FIGS. 7A-12 should be consulted.

The “14273 receptor polypeptide” or “14273 receptor protein” refers tothe polypeptide in SEQ ID NO:1 or SEQ ID NO:4 or encoded by thedeposited cDNA. The term “receptor protein” or “receptor polypeptide”,however, further includes the numerous variants described herein, aswell as fragments derived from the full length 14273 polypeptide andvariants.

The present invention thus provides an isolated or purified 14273receptor polypeptide and variants and fragments thereof.

The human 14273 polypeptide is a 361 residue protein exhibiting threemain structural domains. The amino terminal extracellular domain isidentified to be within residues 1 to about 45 in SEQ ID NO:1. Thetransmembrane domain is identified to be within residues from about 46to about 321 in SEQ ID NO:1. The carboxy terminal intracellular domainis identified to be within residues from about 322 to 361 in SEQ IDNO:1. The transmembrane domain contains seven segments that span themembrane. The transmembrane segments are found from about amino acid 46to about amino acid 66, from about amino acid 75 to about amino acid 98,from about amino acid 113 to about amino acid 134, from about amino acid156 to about amino acid 177, from about amino acid 209 to about aminoacid 227, from about amino acid 266 to about amino acid 289, and fromabout amino acid 297 to about amino acid 321 of SEQ ID NO:1. Within theregion spanning the entire transmembrane domain are three intracellularand three extracellular loops. The three intracellular loops are foundfrom about amino acid 67 to about amino acid 74, from about amino acid135 to about amino acid 155, and from about amino acid 228 to aboutamino acid 265 of SEQ ID NO:1. The three extracellular loops are foundat from about amino acid 99 to about amino acid 112, from about aminoacid 178 to about amino acid 208, and from about amino acid 290 to aboutamino acid 296 of SEQ ID NO:1.

The transmembrane domain includes a GPCR signal transduction signature,ERM, at residues 135-137 of SEQ ID NO:1. The sequence includes anarginine at residue 136 of SEQ ID NO:1, an invariant amino acid inGPCRs.

Based on a BLAST search, highest homology was shown to galaninreceptors. Galanin receptors include the GAL I, GAL II, and GAL IIIreceptors. Significant homology was also found with chemokine receptorsand somatostatin receptors.

As used herein, a polypeptide is said to be “isolated” or “purified”when it is substantially free of cellular material when it is isolatedfrom recombinant and non-recombinant cells, or free of chemicalprecursors or other chemicals when it is chemically synthesized. Apolypeptide, however, can be joined to another polypeptide with which itis not normally associated in a cell and still be considered “isolated”or “purified.”

The receptor polypeptides can be purified to homogeneity. It isunderstood, however, that preparations in which the polypeptide is notpurified to homogeneity are useful and considered to contain an isolatedform of the polypeptide. The critical feature is that the preparationallows for the desired function of the polypeptide, even in the presenceof considerable amounts of other components. Thus, the inventionencompasses various degrees of purity.

In one embodiment, the language “substantially free of cellularmaterial” includes preparations of the receptor polypeptide having lessthan about 30% (by dry weight) other proteins (i.e., contaminatingprotein), less than about 20% other proteins, less than about 10% otherproteins, or less than about 5% other proteins. When the receptorpolypeptide is recombinantly produced, it can also be substantially freeof culture medium, i.e., culture medium represents less than about 20%,less than about 10%, or less than about 5% of the volume of the proteinpreparation.

The language “substantially free of chemical precursors or otherchemicals” includes preparations of the receptor polypeptide in which itis separated from chemical precursors or other chemicals that areinvolved in its synthesis. In one embodiment, the language“substantially free of chemical precursors or other chemicals” includespreparations of the polypeptide having less than about 30% (by dryweight) chemical precursors or other chemicals, less than about 20%chemical precursors or other chemicals, less than about 10% chemicalprecursors or other chemicals, or less than about 5% chemical precursorsor other chemicals.

In one embodiment, the receptor polypeptide comprises the amino acidsequence shown in SEQ ID NO: 1 or SEQ ID NO:4. However, the inventionalso encompasses sequence variants. Variants include a substantiallyhomologous protein encoded by the same genetic locus in an organism,i.e., an allelic variant. Variants also encompass proteins derived fromother genetic loci in an organism, but having substantial homology tothe 14273 receptor protein of SEQ ID NO:1 or SEQ ID NO:4. Variants alsoinclude proteins substantially homologous to the 14273 receptor proteinbut derived from another organism, i.e., an ortholog. Variants alsoinclude proteins that are substantially homologous to the 14273 receptorprotein that are produced by chemical synthesis. Variants also includeproteins that are substantially homologous to the 14273 receptor proteinthat are produced by recombinant methods. It is understood, however,that variants exclude any amino acid sequences disclosed prior to theinvention.

As used herein, two proteins (or a region of the proteins) aresubstantially homologous when the amino acid sequences are at leastabout 50-55%, 55-60%, typically at least about 70-75%, more typically atleast about 80-85%, and most typically at least about 90-95% or morehomologous. A substantially homologous amino acid sequence, according tothe present invention, will be encoded by a nucleic acid sequencehybridizing to the nucleic acid sequence, or portion thereof, of thesequence shown in SEQ ID NO:2 or SEQ ID NO:5 under stringent conditionsas more fully described below.

To determine the percent identity of two amino acid sequences or of twonucleic acid sequences, the sequences are aligned for optimal comparisonpurposes (e.g., gaps can be introduced in one or both of a first and asecond amino acid or nucleic acid sequence for optimal alignment andnon-homologous sequences can be disregarded for comparison purposes). Ina preferred embodiment, the length of a reference sequence aligned forcomparison purposes is at least 30%, preferably at least 40%, morepreferably at least 50%, even more preferably at least 60%, and evenmore preferably at least 70%, 80%, or 90% of the length of the referencesequence (e.g., when aligning a second sequence to the amino acidsequences herein having 100 amino acid residues, at least 140,preferably at least 180, more preferably at least 250, even morepreferably at least 290, and even more preferably at least 320 aminoacid residues are aligned). The amino acid residues or nucleotides atcorresponding amino acid positions or nucleotide positions are thencompared. When a position in the first sequence is occupied by the sameamino acid residue or nucleotide as the corresponding position in thesecond sequence, then the molecules are identical at that position (asused herein amino acid or nucleic acid “identity” is equivalent to aminoacid or nucleic acid “homology”). The percent identity between the twosequences is a function of the number of identical positions shared bythe sequences, taking into account the number of gaps, and the length ofeach gap, which need to be introduced for optimal alignment of the twosequences.

The invention also encompasses polypeptides having a lower degree ofidentity but having sufficient similarity so as to perform one or moreof the same functions performed by the 14273 polypeptide. Similarity isdetermined by conserved amino acid substitution. Such substitutions arethose that substitute a given amino acid in a polypeptide by anotheramino acid of like characteristics. Conservative substitutions arelikely to be phenotypically silent. Typically seen as conservativesubstitutions are the replacements, one for another, among the aliphaticamino acids Ala, Val, Leu, and Ile; interchange of the hydroxyl residuesSer and Thr, exchange of the acidic residues Asp and Glu, substitutionbetween the amide residues Asn and Gln, exchange of the basic residuesLys and Arg and replacements among the aromatic residues Phe, Tyr.Guidance concerning which amino acid changes are likely to bephenotypically silent are found in Bowie et al., Science 247:1306-1310(1990).

TABLE 1 Conservative Amino Acid Substitutions. Aromatic PhenylalanineTryptophan Tyrosine Hydrophobic Leucine Isoleucine Valine PolarGlutamine Asparagine Basic Arginine Lysine Histidine Acidic AsparticAcid Glutamic Acid Small Alanine Serine Threonine Methionine Glycine

The comparison of sequences and determination of percent identity andsimilarity between two sequences can be accomplished using amathematical algorithm. (Computational Molecular Biology, Lesk, A. M.,ed., Oxford University Press, New York, 1988; Biocomputing: Informaticsand Genome Projects, Smith, D. W., ed., Academic Press, New York, 1993;Computer Analysis of Sequence Data, Part 1, Griffin, A. M., and Griffin,H. G., eds., Humana Press, New Jersey, 1994; Sequence Analysis inMolecular Biology, von Heinje, G., Academic Press, 1987; and SequenceAnalysis Primer, Gribskov, M. and Devereux, J., eds., M Stockton Press,New York, 1991). In a preferred embodiment, the percent identity betweentwo amino acid sequences is determined using the Needleman and Wunsch(J. Mol. Biol. (48):444-453 (1970)) algorithm which has beenincorporated into the GAP program in the GCG software package, usingeither a Blossom 62 matrix or a PAM250 matrix, and a gap weight of 16,14, 12, 10, 8, 6, or 4 and a length weight of 1, 2, 3, 4, 5, or 6. Inyet another preferred embodiment, the percent identity between twonucleotide sequences is determined using the GAP program in the GCGsoftware package (Devereux, J., et al., Nucleic Acids Res. 12(1):387(1984)), using a NWSgapdna.CMP matrix and a gap weight of 40, 50, 60,70, or 80 and a length weight of 1, 2, 3, 4, 5, or 6. In anotherembodiment, the percent identity between two amino acid or nucleotidesequences is determined using the algorithm of E. Meyers and W. Miller(CABIOS, 4:11-17 (1989)) which has been incorporated into the ALIGNprogram (version 2.0), using a PAM120 weight residue table, a gap lengthpenalty of 12 and a gap penalty of 4.

The nucleic acid and protein sequences of the present invention canfurther be used as a “query sequence” to perform a search against publicdatabases to, for example, identify other family members or relatedsequences. Such searches can be performed using the NBLAST and XBLASTprograms (version 2.0) of Altschul, et al. (1990) J. Mol. Biol.215:403-10. BLAST nucleotide searches can be performed with the NBLASTprogram, score=100, wordlength=12 to obtain nucleotide sequenceshomologous to the nucleic acid molecules of the invention. BLAST proteinsearches can be performed with the XBLAST program, score=50,wordlength=3 to obtain amino acid sequences homologous to the proteinsof the invention. To obtain gapped alignments for comparison purposes,Gapped BLAST can be utilized as described in Altschul et al., (1997)Nucleic Acids Res. 25(17):3389-3402. When utilizing BLAST and GappedBLAST programs, the default parameters of the respective programs (e.g.,XBLAST and NBLAST) can be used.

A variant polypeptide can differ in amino acid sequence by one or moresubstitutions, deletions, insertions, inversions, fusions, andtruncations or a combination of any of these.

Variant polypeptides can be fully functional or can lack function in oneor more activities. Thus, in the present case, variations can affect thefunction, for example, of one or more of the regions corresponding toligand binding, membrane association, G-protein binding and signaltransduction.

Fully functional variants typically contain only conservative variationor variation in non-critical residues or in non-critical regions.Functional variants can also contain substitution of similar amino acidswhich result in no change or an insignificant change in function.Alternatively, such substitutions may positively or negatively affectfunction to some degree.

Non-functional variants typically contain one or more non-conservativeamino acid substitutions, deletions, insertions, inversions, ortruncation or a substitution, insertion, inversion, or deletion in acritical residue or critical region.

As indicated, variants can be naturally-occurring or can be made byrecombinant means or chemical synthesis to provide useful and novelcharacteristics for the receptor polypeptide. This includes preventingimmunogenicity from pharmaceutical formulations by preventing proteinaggregation.

Useful variations further include alteration of ligand bindingcharacteristics. For example, one embodiment involves a variation at thebinding site that results in binding but not release, or slower release,of ligand. A further useful variation at the same sites can result in ahigher affinity for ligand. Useful variations also include changes thatprovide for affinity for another ligand. Another useful variationincludes one that allows binding but which prevents activation by theligand. Another useful variation includes variation in the transmembraneG-protein-binding/signal transduction domain that provides for reducedor increased binding by the appropriate G-protein or for binding by adifferent G-protein than the one with which the receptor is normallyassociated. Another useful variation provides a fusion protein in whichone or more domains or subregions is operationally fused to one or moredomains or subregions from another G-protein coupled receptor.

Amino acids that are essential for function can be identified by methodsknown in the art, such as site-directed mutagenesis or alanine-scanningmutagenesis (Cunningham et al., Science 244:1081-1085 (1989)). Thelatter procedure introduces single alanine mutations at every residue inthe molecule. The resulting mutant molecules are then tested forbiological activity such as receptor binding or in vitro, or in vitroproliferative activity. Sites that are critical for ligand-receptorbinding can also be determined by structural analysis such ascrystallization, nuclear magnetic resonance or photoaffinity labeling(Smith et al., J. Mol. Biol. 224:899-904 (1992); de Vos et al. Science255:306-312 (1992)).

Substantial homology can be to the entire nucleic acid or amino acidsequence or to fragments of these sequences.

The invention thus also includes polypeptide fragments of the 14273receptor protein. Fragments can be derived from the amino acid sequenceshown in SEQ ID NO:1 or SEQ ID NO:4. However, the invention alsoencompasses fragments of the variants of the 14273 receptor protein asdescribed herein.

As used herein, a fragment comprises at least 6 contiguous amino acidsfrom amino acid 1-127 of SEQ ID NO:1 or SEQ ID NO:4, at least 9 aminoacids from amino acid 1 to about amino acid 184 of SEQ ID NO:1 or SEQ IDNO:4, greater than 10 amino acids from amino acid 1 to about amino acid210 of SEQ ID NO:1 or SEQ ID NO:4, and fragments greater than 32 aminoacids from amino acid 1 to about amino acid 291 of SEQ ID NO:1 or SEQ IDNO:4. Specific fragments also include fragments greater than those foundfrom amino acid 123-132, 134-141, 162-167, 177-186, 203-237, 238-242,244-259, 261-292, 295-323, 332-337, 339-345, and 347-351 of SEQ ID NO:1or SEQ ID NO:4.

Fragments can retain one or more of the biological activities of theprotein, for example the ability to bind to a G-protein or ligand.Fragments can also be useful as an immunogen to generate receptorantibodies.

Biologically active fragments can comprise a domain or motif, e.g., anextracellular or intracellular domain or loop, one or more transmembranesegments, or parts thereof, G-protein binding site, or GPCR signature,glycosylation, myristoylation, amidation, and phosphorylation sites, andsites showing a leucine zipper pattern L [a-z] {6} L [a-z] {6} L[a-z]{6} L sites. Such peptides can be, for example, 6, 10, 15, 20, 30, 35,36, 37, 38, 39, 40, 50, 100 or more amino acids in length.

Possible fragments of the human receptor include, but are not limitedto: 1) soluble peptides comprising the entire amino terminalextracellular domain about amino acid 1 to about amino acid 45 of SEQ IDNO:1, or parts thereof; 2) peptides comprising the entire carboxyterminal intracellular domain from about amino acid 322 to amino acid361 of SEQ ID NO:1, or parts thereof; 3) peptides comprising the regionspanning the entire transmembrane domain from about amino acid 46 toabout amino acid 321 of SEQ ID NO:1, or parts thereof; 4) any of thespecific transmembrane segments, or parts thereof, from about amino acid46 to about amino acid 66, from about amino acid 75 to about amino acid98, from about amino acid 113 to about amino acid 134, from about aminoacid 156 to about amino acid 177, from about amino acid 209 to aboutamino acid 227, from about amino acid 266 to about amino acid 289, andfrom about amino acid 297 to about amino acid 321 of SEQ ID NO:1; 5) anyof the three intracellular or three extracellular loops, or partsthereof, from about amino acid 67 to about amino acid 74, from aboutamino acid 135 to about amino acid 155, from about amino acid 228 toabout amino acid 265, from about amino acid 99 to about amino acid 112,from about amino acid 178 to about amino acid 208, and from about aminoacid 290 to about amino acid 296 of SEQ ID NO:1. Fragments furtherinclude combinations of the above fragments, such as an amino terminaldomain combined with one or more transmembrane segments and theattendant extra or intracellular loops or one or more transmembranesegments, and the attendant intra or extracellular loops, plus thecarboxy terminal domain. Thus, any of the above fragments can becombined. Other fragments include the mature protein from about aminoacid 37 to 361 of SEQ ID NO:1. Other fragments contain the variousfunctional sites described herein and a sequence containing the GPCRsignature sequence. Fragments, for example, can extend in one or bothdirections from the functional site to encompass 5, 10, 15, 20, 30, 40,50, or up to 100 amino acids. Further, fragments can includesub-fragments of the specific domains mentioned above, whichsub-fragments retain the function of the domain from which they arederived.

Fragments also include antigenic fragments and specifically those shownto have a high antigenic index in FIGS. 3 and 9.

Accordingly, possible fragments include fragments defining aligand-binding site, fragments defining a glycosylation, amidation,phosphorylation, or myristoylation site, fragments defining membraneassociation, fragments defining interaction with G proteins and signaltransduction, and fragments defining leucine zipper sites. By this isintended a discrete fragment that provides the relevant function orallows the relevant function to be identified. In a preferredembodiment, the fragment contains the ligand-binding site.

The invention also provides fragments with immunogenic properties. Thesecontain an epitope-bearing portion of the 14273 receptor protein andvariants. These epitope-bearing peptides are useful to raise antibodiesthat bind specifically to a receptor polypeptide or region or fragment.These peptides can contain at least 6, 12, at least 14, or between atleast about 15 to about 30 amino acids.

Non-limiting examples of antigenic polypeptides that can be used togenerate antibodies include peptides derived from the amino terminalextracellular domain or any of the extracellular loops. Regions having ahigh antigenicity index are shown in FIGS. 3 and 9. However,intracellularly-made antibodies (“intrabodies”) are also encompassed,which would recognize intracellular receptor peptide regions.

The fragments to which the invention pertains, however, are not to beconstrued as encompassing fragments that may be disclosed prior to thepresent invention.

The receptor polypeptides (including variants and fragments which mayhave been disclosed prior to the present invention) are useful forbiological assays related to GPCRs. Such assays involve any of the knownGPCR functions or activities or properties useful for diagnosis andtreatment of GPCR-related conditions.

The epitope-bearing receptor and polypeptides may be produced by anyconventional means (Houghten, R. A., Proc. Natl. Acad. Sci. USA82:5131-5135 (1985)). Simultaneous multiple peptide synthesis isdescribed in U.S. Pat. No. 4,631,211.

Fragments can be discrete (not fused to other amino acids orpolypeptides) or can be within a larger polypeptide. Further, severalfragments can be comprised within a single larger polypeptide. In oneembodiment a fragment designed for expression in a host can haveheterologous pre- and pro-polypeptide regions fused to the aminoterminus of the receptor fragment and an additional region fused to thecarboxyl terminus of the fragment.

The invention thus provides chimeric or fusion proteins. These comprisea receptor protein operatively linked to a heterologous protein havingan amino acid sequence not substantially homologous to the receptorprotein. “Operatively linked” indicates that the receptor protein andthe heterologous protein are fused in-frame. The heterologous proteincan be fused to the N-terminus or C-terminus of the receptor protein.

In one embodiment the fusion protein does not affect receptor functionper se. For example, the fusion protein can be a GST-fusion protein inwhich the receptor sequences are fused to the C-terminus of the GSTsequences. Other types of fusion proteins include, but are not limitedto, enzymatic fusion proteins, for example beta-galactosidase fusions,yeast two-hybrid GAL fusions, poly-His fusions and Ig fusions. Suchfusion proteins, particularly poly-His fusions, can facilitate thepurification of recombinant receptor protein. In certain host cells(e.g., mammalian host cells), expression and/or secretion of a proteincan be increased by using a heterologous signal sequence. Therefore, inanother embodiment, the fusion protein contains a heterologous signalsequence at its N-terminus.

EP-A-O 464 533 discloses fusion proteins comprising various portions ofimmunoglobulin constant regions. The Fc is useful in therapy anddiagnosis and thus results, for example, in improved pharmacokineticproperties (EP-A 0232 262). In drug discovery, for example, humanproteins have been fused with Fc portions for the purpose ofhigh-throughput screening assays to identify antagonists. Bennett et al.(J. Mol. Recog. 8:52-58 (1995)) and Johanson et al. (J. Biol. Chem. 270,16:9459-9471 (1995)). Thus, this invention also encompasses solublefusion proteins containing a receptor polypeptide and various portionsof the constant regions of heavy or light chains of immunoglobulins ofvarious subclass (IgG, IgM, IgA, IgE). Preferred as immunoglobulin isthe constant part of the heavy chain of human IgG, particularly IgG1,where fusion takes place at the hinge region. For some uses it isdesirable to remove the Fc after the fusion protein has been used forits intended purpose, for example when the fusion protein is to be usedas antigen for immunizations. In a particular embodiment, the Fc partcan be removed in a simple way by a cleavage sequence which is alsoincorporated and can be cleaved with factor Xa.

A chimeric or fusion protein can be produced by standard recombinant DNAtechniques. For example, DNA fragments coding for the different proteinsequences are ligated together in-frame in accordance with conventionaltechniques. In another embodiment, the fusion gene can be synthesized byconventional techniques including automated DNA synthesizers.Alternatively, PCR amplification of gene fragments can be carried outusing anchor primers which give rise to complementary overhangs betweentwo consecutive gene fragments which can subsequently be annealed andre-amplified to generate a chimeric gene sequence (see Ausubel et al.,Current Protocols in Molecular Biology, 1992). Moreover, many expressionvectors are commercially available that already encode a fusion moiety(e.g., a GST protein). A receptor protein-encoding nucleic acid can becloned into such an expression vector such that the fusion moiety islinked in-frame to the receptor protein.

Another form of fusion protein is one that directly affects receptorfunctions. Accordingly, a receptor polypeptide is encompassed by thepresent invention in which one or more of the receptor domains (or partsthereof) has been replaced by homologous domains (or parts thereof) fromanother G-protein coupled receptor or other type of receptor.Accordingly, various permutations are possible. The amino terminalextracellular domain, or subregion thereof (for example,ligand-binding), can be replaced with the domain or subregion fromanother ligand-binding receptor protein. Alternatively, the entiretransmembrane domain or any of the seven segments or loops, or partsthereof, for example, G-protein-binding/signal transduction, can bereplaced. Finally, the carboxy terminal intracellular domain orsubregion can be replaced. Thus, chimeric receptors can be formed inwhich one or more of the native domains or subregions has been replaced.

The isolated receptor protein can be purified from cells that naturallyexpress it, such as from fetal brain, heart, skeletal muscle, thymus,prostate, placenta, and uterus, where expression of the receptor hasbeen detected, especially in heart and skeletal muscle, purified fromcells that have been altered to express it (recombinant), or synthesizedusing known protein synthesis methods. Preferred embodiments includeisolation from recombinant cardiomyocytes or from diseasedcardiomyocytes overexpressing a normal receptor gene or expressing areceptor variant. Variants that are correlated with cardiovasculardiseases can be isolated from affected tissues or from at-riskindividuals. Alternatively, such variants can be produced by chemicalsynthesis or by site-directed mutagenesis.

In one embodiment, the protein is produced by recombinant DNAtechniques. For example, a nucleic acid molecule encoding the receptorpolypeptide is cloned into an expression vector, the vector isintroduced into a host cell and the protein is expressed in the hostcell. The protein can then be isolated from the cells by an appropriatepurification scheme using standard protein purification techniques.

Polypeptides often contain amino acids other than the 20 amino acidscommonly referred to as the 20 naturally-occurring amino acids. Further,many amino acids, including the terminal amino acids, may be modified bynatural processes, such as processing and other post-translationalmodifications, or by chemical modification techniques well known in theart. Common modifications that occur naturally in polypeptides aredescribed in basic texts, detailed monographs, and the researchliterature, and they are well known to those of skill in the art.

Accordingly, the polypeptides also encompass derivatives or analogs inwhich a substituted amino acid residue is not one encoded by the geneticcode, in which a substituent group is included, in which the maturepolypeptide is fused with another compound, such as a compound toincrease the half-life of the polypeptide (for example, polyethyleneglycol), or in which the additional amino acids are fused to the maturepolypeptide, such as a leader or secretory sequence or a sequence forpurification of the mature polypeptide or a pro-protein sequence.

Known modifications include, but are not limited to, acetylation,acylation, ADP-ribosylation, amidation, covalent attachment of flavin,covalent attachment of a heme moiety, covalent attachment of anucleotide or nucleotide derivative, covalent attachment of a lipid orlipid derivative, covalent attachment of phosphatidylinositol,cross-linking, cyclization, disulfide bond formation, demethylation,formation of covalent crosslinks, formation of cystine, formation ofpyroglutamate, formylation, gamma carboxylation, glycosylation, GPIanchor formation, hydroxylation, iodination, methylation,myristoylation, oxidation, proteolytic processing, phosphorylation,prenylation, racemization, selenoylation, sulfation, transfer-RNAmediated addition of amino acids to proteins such as arginylation, andubiquitination.

Such modifications are well-known to those of skill in the art and havebeen described in great detail in the scientific literature. Severalparticularly common modifications, glycosylation, lipid attachment,sulfation, gamma-carboxylation of glutamic acid residues, hydroxylationand ADP-ribosylation, for instance, are described in most basic texts,such as Proteins—Structure and Molecular Properties, 2nd Ed., T. E.Creighton, W. H. Freeman and Company, New York (1993). Many detailedreviews are available on this subject, such as by Wold, F.,Posttranslational Covalent Modification of Proteins, B. C. Johnson, Ed.,Academic Press, New York 1-12 (1983); Seifter et al. (Meth. Enzymol.182: 626-646 (1990)) and Rattan et al. (Ann. N.Y. Acad. Sci. 663:48-62(1992)).

As is also well known, polypeptides are not always entirely linear. Forinstance, polypeptides may be branched as a result of ubiquitination,and they may be circular, with or without branching, generally as aresult of post-translation events, including natural processing eventand events brought about by human manipulation which do not occurnaturally. Circular, branched and branched circular polypeptides may besynthesized by non-translational natural processes and by syntheticmethods.

Modifications can occur anywhere in a polypeptide, including the peptidebackbone, the amino acid side-chains and the amino or carboxyl termini.Blockage of the amino or carboxyl group in a polypeptide, or both, by acovalent modification, is common in naturally-occurring and syntheticpolypeptides. For instance, the amino terminal residue of polypeptidesmade in E. coli, prior to proteolytic processing, almost invariably willbe N-formylmethionine.

The modifications can be a function of how the protein is made. Forrecombinant polypeptides, for example, the modifications will bedetermined by the host cell posttranslational modification capacity andthe modification signals in the polypeptide amino acid sequence.Accordingly, when glycosylation is desired, a polypeptide should beexpressed in a glycosylating host, generally a eukaryotic cell. Insectcells often carry out the same posttranslational glycosylations asmammalian cells and, for this reason, insect cell expression systemshave been developed to efficiently express mammalian proteins havingnative patterns of glycosylation. Similar considerations apply to othermodifications.

The same type of modification may be present in the same or varyingdegree at several sites in a given polypeptide. Also, a givenpolypeptide may contain more than one type of modification.

Polypeptide Uses

Expression of the 14273 receptor has been associated by the inventorswith cardiovascular diseases. mRNA screening of normal and diseasedhuman tissues showed the induction of receptor mRNA in hypertrophiccardiac myocytes. This induction is associated with morphologicalchange. In a transgenic mouse model in which the receptor isspecifically overexpressed in cardiomyocytes, the overexpression resultsin cardiomyocyte enlargement. In several independently generatedtransgenic mouse models, the mice developed cardiomyocyte hypertrophy,many of these mice dying from heart failure. Histological analysis ofhearts from these animals showed biventricular dilatation, cardiomyocytehypertrophy, interstitial fibrosis and atrial thrombi. The heart:bodyweight ratio was increased. In one series the ratio ranged fromapproximately 1.5-2.7. Enlargement of the hearts, thrombosis in theatrium, edema in the chest, and breathing difficulties, were observed.Accordingly, any of the specific uses described herein include thecontext of cardiovascular diseases or a predisposition for developingcardiovascular diseases, for example, the cardiovascular diseasesdiscussed herein as associated with receptor expression.

The receptor polypeptides are useful for producing antibodies specificfor the 14273 receptor protein, regions, or fragments. Regions having ahigh antigenicity index score are shown in FIGS. 3 and 9. For example,modified receptor polypeptides isolated from diseased tissues can beused to prepare antibodies, which are then useful for screening for geneexpression in diseased tissues in vitro or in vivo, modulating geneexpression, and treating disorders associated with the receptorpolypeptides, especially cardiovascular diseases. Modified receptorpolypeptides prepared by chemical synthesis or by such techniques assite-directed mutagenesis, if found to be pertinent to a disorder suchas cardiovascular diseases, can also be used to prepare antibodies forscreening and modulation.

In one embodiment, an antibody was developed against a C-terminalantigenic segment (amino acids 348-361), DTSVKRNDLSIISG. This antibodywas successfully used to show the overexpression of the receptor intransgenic mice containing the receptor gene and specifically incardiomyocytes. The antibody did not bind to control samples notcontaining and/or expressing the gene for the receptor.

The receptor polypeptides (including variants and fragments which mayhave been disclosed prior to the present invention) are useful forbiological assays related to GPCRs. Such assays involve any of the knownGPCR functions or activities or properties useful for diagnosis andtreatment of GPCR-related conditions. Diseased tissue, such as cardiactissue, skeletal muscle, uterus, thymus, and prostate, can be used toidentify modified receptor polypeptides which then serve as a basis fordiagnosis and for rational drug design.

The receptor polypeptides are also useful in drug screening assays, incell-based or cell-free systems. Cell-based systems can be native, i.e.,cells that normally express the receptor protein, as a biopsy orexpanded in cell culture. In one embodiment, however, cell-based assaysinvolve recombinant host cells expressing the receptor protein. Diseasedtissue, specifically, diseased cardiac tissue (such as diseased heart),skeletal muscle, thymus, uterus, and prostate, are useful to screen fordrugs that can be used in affecting the diseased tissue. Preferred cellsinclude, but are not limited to, cardiac myocytes, and especiallyhypertrophic cardiac myocytes. The effect of the drug can be scoredbased on, among other things, morphological change.

Cardiomyocytes for drug screening assays can be normal or can be derivedfrom patients having cardiovascular disease or having a predispositionto such disease. Accordingly, cardiomyocytes can be enlarged or derivedfrom a patient having a tendency to produce such enlargedcardiomyocytes. These cardiomyocytes can thus be tested for agents thataffect the biochemistry of the cardiomyocytes by affecting the receptorgene or gene product. These cardiomyocytes can be further modified byrecombinant DNA techniques to add or delete copies of receptor genesequences or to introduce altered sequences. Thus they can be used as abasis for performing genetic therapy. Alternatively, drug screening canbe performed with originally normal cardiomyocytes that have beenmodified by recombinant DNA techniques to overexpress receptor proteinor RNA and/or express variant receptor protein or RNA.

Drug screening assays can also be performed in transgenic animal modelssuch as those described herein. Thus, naturally-occurring mutants ormutants made in a laboratory can be used to create transgenic animalsthat serve as a basis for drug screening. This model is particularlyuseful in assessing the total effect of an in vivo environment on theeffect of a given drug. These animals can serve as an animal model fordisease, such as cardiovascular diseases, so that in addition toascertaining an effect on the specific mutant, an effect can beascertained on the total system. Transgenic animals can thus be createdthat overexpress the receptor protein or express a variant, leading to,for example, cardiomyocyte hypertrophy. Alternatively, such animals canbe created that underexpress the receptor or, in the case of “knockout”mice, lack one or more copies of the gene. Variant genes include all ofthe modifications described herein, such as insertion, deletion, andnucleotide substitutions. In one embodiment, gene expression is underthe control of an inducible promoter. Therefore, modulation of the geneand, thus, modulation of the disease state is provided. The inventionthus also encompasses cardiomyocytes derived from transgenic animals inwhich the cardiovascular disease has been produced by means ofexpression of the receptor in recombinant host cells, is naturallyoccurring, or occurs as the result of other protocols and/or agents.

The polypeptides can be used to identify compounds that modulatereceptor activity. Both 14273 protein and appropriate variants andfragments can be used in high-throughput screens to assay candidatecompounds for the ability to bind to the receptor. These compounds canbe further screened against a functional receptor to determine theeffect of the compound on the receptor activity. Compounds can beidentified that activate (agonist) or inactivate (antagonist) thereceptor to a desired degree.

The terms “agonist” and “antagonist” represent compounds that enhance ordiminish a response. As one form of an agonist, the compound binds tothe same site as the endogenous compound and produces the same type ofsignal, usually of equal or greater magnitude than the endogenous agent.Another form of agonist binds to a different site than the firstagonist, producing no signal by itself; however, an enhanced signal isgenerated when the endogenous agent also binds to its site. This iscalled an allosteric action. One form of antagonist binds to the siteused by the endogenous agent and diminishes or blocks the signalgenerated by the endogenous agent. Another form of antagonist binds toan allosteric site, similar to the second form of agonist, but producesa diminished signal generated by the endogenous agent. A third form ofantagonist dissolves in the membrane or crosses the membrane andintercepts the signal generated by the endogenous agent within themembrane or on the intracellular side. An antagonist, accordingly,encompasses negative agonists or “inverse agonists”, having a negativeintrinsic activity that reduces the receptor signal activity relative tothe signaling activity measured in the absence of the inverse agonist.Such an antagonist is distinguished from an antagonist having nointrinsic activity and no effect on the receptor's basal activity. Thus,for example, an inverse agonist could alter the receptor confirmation,thereby reducing or eliminating interaction with a ligand. See, Milliganet al., TIPS 16:10 (1995).

The receptor polypeptides can be used to screen a compound for theability to stimulate or inhibit interaction between the receptor proteinand a target molecule that normally interacts with the receptor protein.The target can be ligand or a component of the signal pathway with whichthe receptor protein normally interacts (for example, a G-protein orother interactor involved in cAMP or phosphatidylinositol turnoverand/or adenylate cyclase, or phospholipase C activation). The assayincludes the steps of combining the receptor protein with a candidatecompound under conditions that allow the receptor protein or fragment tointeract with the target molecule, and to detect the formation of acomplex between the protein and the target or to detect the biochemicalconsequence of the interaction with the receptor protein and the target,such as any of the associated effects of signal transduction, such asion flux, G-protein phosphorylation, cyclic AMP or phosphatidylinositolturnover, and adenylate cyclase or phospholipase C activation.

The receptor polypeptides are useful in cell based assays when they areoverexpressed in a cell. Accordingly, such cells overexpressing thereceptor are useful to identify compounds that are capable of modulatingor compensating for the overexpression. Cells overexpressing thereceptor can be derived from natural sources or can be created byroutine recombinant methods.

The receptor polypeptides are also useful for screening compounds in acell based assay when constitutively activated on a cell. Such cellsexpressing constitutively activated receptors are useful for screeningcompounds that modulate receptor activation. Such cells can be derivedfrom natural sources or can be created by recombinant means that arewell known in the art. For example, see Scheer et al., J. ReceptorSignal Transduction Res. 17:57-73 (1997); U.S. Pat. No. 5,750,353.

Candidate compounds include, for example, 1) peptides such as solublepeptides, including Ig-tailed fusion peptides and members of randompeptide libraries (see, e.g., Lam et al., Nature 354:82-84 (1991);Houghten et al., Nature 354:84-86 (1991)) and combinatorialchemistry-derived molecular libraries made of D- and/or L-configurationamino acids; 2) phosphopeptides (e.g., members of random and partiallydegenerate, directed phosphopeptide libraries, see, e.g., Songyang etal., Cell 72:767-778 (1993)); 3) antibodies (e.g., polyclonal,monoclonal, humanized, anti-idiotypic, chimeric, and single chainantibodies as well as Fab, F(ab′)₂, Fab expression library fragments,and epitope-binding fragments of antibodies); and 4) small organic andinorganic molecules (e.g., molecules obtained from combinatorial andnatural product libraries).

One candidate compound is a soluble full-length receptor or fragmentthat competes for ligand binding. Other candidate compounds includemutant receptors or appropriate fragments containing mutations thataffect receptor function and thus compete for ligand. Accordingly, afragment that competes for ligand, for example with a higher affinity,or a fragment that binds ligand but does not allow release, isencompassed by the invention.

The invention provides other end points to identify compounds thatmodulate (stimulate or inhibit) receptor activity. The assays typicallyinvolve an assay of events in the signal transduction pathway thatindicate receptor activity. Thus, the expression of genes that are up-or down-regulated in response to the receptor protein dependent signalcascade can be assayed. In one embodiment, the regulatory region of suchgenes can be operably linked to a marker that is easily detectable, suchas luciferase. Alternatively, phosphorylation of the receptor protein,or a receptor protein target, could also be measured.

It is also understood that a disorder caused by aberrant levels ormutations in the protein can be used as a basis for an endpoint.Accordingly, specific deviations in the development or course of thedisorder in response to a compound that acts on the receptor can serveas an endpoint.

Any of the biological or biochemical functions mediated by the receptorcan be used as an endpoint assay. These include all of the biochemicalor biochemical/biological events described herein, in the referencescited herein, incorporated by reference for these endpoint assaytargets, and other functions known to those of ordinary skill in theart. These endpoints include, but are not limited to, cardiomyocyteenlargement, gross enlargement of the heart, including enlargement ofthe atrium, atrial thrombi, chest edema, biventricular dilatation, andinterstitial fibrosis.

Binding and/or activating compounds can also be screened by usingchimeric receptor proteins in which the amino terminal extracellulardomain, or parts thereof, the entire transmembrane domain or subregions,such as any of the seven transmembrane segments or any of theintracellular or extracellular loops and the carboxy terminalintracellular domain, or parts thereof, can be replaced by heterologousdomains or subregions. For example, a G-protein-binding region can beused that interacts with a different G-protein then that which isrecognized by the native receptor. Accordingly, a different set ofsignal transduction components is available as an end-point assay foractivation. Alternatively, the entire transmembrane portion orsubregions (such as transmembrane segments or intracellular orextracellular loops) can be replaced with the entire transmembraneportion or subregions specific to a host cell that is different from thehost cell from which the amino terminal extracellular domain and/or theG-protein-binding region are derived. This allows for assays to beperformed in other than the specific host cell from which the receptoris derived. Alternatively, the amino terminal extracellular domain(and/or other ligand-binding regions) could be replaced by a domain(and/or other binding region) binding a different ligand, thus,providing an assay for test compounds that interact with theheterologous amino terminal extracellular domain (or region) but stillcause signal transduction. Finally, activation can be detected by areporter gene containing an easily detectable coding region operablylinked to a transcriptional regulatory sequence that is part of thenative signal transduction pathway.

The receptor polypeptides are also useful in competition binding assaysin methods designed to discover compounds that interact with thereceptor. Thus, a compound is exposed to a receptor polypeptide underconditions that allow the compound to bind or to otherwise interact withthe polypeptide. Soluble receptor polypeptide is also added to themixture. If the test compound interacts with the soluble receptorpolypeptide, it decreases the amount of complex formed or activity fromthe receptor target. This type of assay is particularly useful in casesin which compounds are sought that interact with specific regions of thereceptor. Thus, the soluble polypeptide that competes with the targetreceptor region is designed to contain peptide sequences correspondingto the region of interest.

To perform cell-free drug screening assays, it is desirable toimmobilize either the receptor protein, or fragment, or its targetmolecule to facilitate separation of complexes from uncomplexed forms ofone or both of the proteins, as well as to accommodate automation of theassay.

Techniques for immobilizing proteins on matrices can be used in the drugscreening assays. In one embodiment, a fusion protein can be providedwhich adds a domain that allows the protein to be bound to a matrix. Forexample, glutathione-S-transferase/14273 fusion proteins can be adsorbedonto glutathione sepharose beads (Sigma Chemical, St. Louis, Mo.) orglutathione derivatized microtitre plates, which are then combined withthe cell lysates (e.g., ³⁵S-labeled) and the candidate compound, and themixture incubated under conditions conducive to complex formation (e.g.,at physiological conditions for salt and pH). Following incubation, thebeads are washed to remove any unbound label, and the matrix immobilizedand radiolabel determined directly, or in the supernatant after thecomplexes are dissociated. Alternatively, the complexes can bedissociated from the matrix, separated by SDS-PAGE, and the level ofreceptor-binding protein found in the bead fraction quantitated from thegel using standard electrophoretic techniques. For example, either thepolypeptide or its target molecule can be immobilized utilizingconjugation of biotin and streptavidin using techniques well known inthe art. Alternatively, antibodies reactive with the protein but whichdo not interfere with binding of the protein to its target molecule canbe derivatized to the wells of the plate, and the protein trapped in thewells by antibody conjugation. Preparations of a receptor-bindingprotein and a candidate compound are incubated in the receptorprotein-presenting wells and the amount of complex trapped in the wellcan be quantitated. Methods for detecting such complexes, in addition tothose described above for the GST-immobilized complexes, includeimmunodetection of complexes using antibodies reactive with the receptorprotein target molecule, or which are reactive with receptor protein andcompete with the target molecule; as well as enzyme-linked assays whichrely on detecting an enzymatic activity associated with the targetmolecule.

Modulators of receptor protein activity identified according to thesedrug screening assays can be used to treat a subject with a disordermediated by the receptor pathway, by treating cells that express the14273 protein, such as in heart, skeletal muscle, thymus, prostate, anduterus. These methods of treatment include the steps of administeringthe modulators of protein activity in a pharmaceutical composition asdescribed herein, to a subject in need of such treatment. Preferredcells include, but are not limited to, cardiomyocytes, and particularlyenlarged cardiomyocytes.

The receptor polypeptides also are useful to provide a target fordiagnosing a disease or predisposition to disease mediated by thereceptor protein, especially in heart, skeletal muscle, thymus, uterus,and prostate. The heart is an especially preferred target, andparticularly cardiac myocytes, which have been shown by the inventors assubject to hypertrophy as a result of overexpression of the receptorprotein. Accordingly, methods are provided for detecting the presence,or levels of, the receptor protein in a cell, tissue, or organism. Themethod involves contacting a biological sample with a compound capableof interacting with the receptor protein such that the interaction canbe detected.

One agent for detecting receptor protein is an antibody capable ofselectively binding to receptor protein. A biological sample includestissues, cells and biological fluids isolated from a subject, as well astissues, cells and fluids present within a subject.

The receptor protein also provides a target for diagnosing activedisease, or predisposition to disease, in a patient having a variantreceptor protein. Thus, receptor protein can be isolated from abiological sample, assayed for the presence of a genetic mutation thatresults in aberrant receptor protein. This includes amino acidsubstitution, deletion, insertion, rearrangement, (as the result ofaberrant splicing events), and inappropriate post-translationalmodification. Analytic methods include altered electrophoretic mobility,altered tryptic peptide digest, altered receptor activity in cell-basedor cell-free assay, alteration in ligand or antibody-binding pattern,altered isoelectric point, direct amino acid sequencing, and any otherof the known assay techniques useful for detecting mutations in aprotein.

In vitro techniques for detection of receptor protein include enzymelinked immunosorbent assays (ELISAs), Western blots,immunoprecipitations and immunofluorescence. Alternatively, the proteincan be detected in vivo in a subject by introducing into the subject alabeled anti-receptor antibody. For example, the antibody can be labeledwith a radioactive marker whose presence and location in a subject canbe detected by standard imaging techniques. Particularly useful aremethods which detect the alletic variant of a receptor protein expressedin a subject and methods which detect fragments of a receptor protein ina sample.

The receptor polypeptides are also useful in pharmacogenomic analysis.Pharmacogenomics deal with clinically significant hereditary variationsin the response to drugs due to altered drug disposition and abnormalaction in affected persons. See, e.g., Eichelbaum, M., Clin. Exp.Pharmacol. Physiol. 23(10-11):983-985 (1996), and Linder, M. W., Clin.Chem. 43(2):254-266 (1997). The clinical outcomes of these variationsresult in severe toxicity of therapeutic drugs in certain individuals ortherapeutic failure of drugs in certain individuals as a result ofindividual variation in metabolism. Thus, the genotype of the individualcan determine the way a therapeutic compound acts on the body or the waythe body metabolizes the compound. Further, the activity of drugmetabolizing enzymes effects both the intensity and duration of drugaction. Thus, the pharmacogenomics of the individual permit theselection of effective compounds and effective dosages of such compoundsfor prophylactic or therapeutic treatment based on the individual'sgenotype. The discovery of genetic polymorphisms in some drugmetabolizing enzymes has explained why some patients do not obtain theexpected drug effects, show an exaggerated drug effect, or experienceserious toxicity from standard drug dosages. Polymorphisms can beexpressed in the phenotype of the extensive metabolizer and thephenotype of the poor metabolizer. Accordingly, genetic polymorphism maylead to allelic protein variants of the receptor protein in which one ormore of the receptor functions in one population is different from thosein another population. The polypeptides thus allow a target to ascertaina genetic predisposition that can affect treatment modality. Thus, in aligand-based treatment, polymorphism may give rise to amino terminalextracellular domains and/or other ligand-binding regions that are moreor less active in ligand binding, and receptor activation. Accordingly,ligand dosage would necessarily be modified to maximize the therapeuticeffect within a given population containing a polymorphism. As analternative to genotyping, specific polymorphic polypeptides could beidentified.

The receptor polypeptides are also useful for monitoring therapeuticeffects during clinical trials and other treatment. Thus, thetherapeutic effectiveness of an agent that is designed to increase ordecrease gene expression, protein levels or receptor activity can bemonitored over the course of treatment using the receptor polypeptidesas an end-point target.

The receptor polypeptides are also useful for treating areceptor-associated disorder. Accordingly, methods for treatment includethe use of soluble receptor or fragments of the receptor protein thatcompete for ligand binding. These receptors or fragments can have ahigher affinity for the ligand so as to provide effective competition.

Antibodies

The invention also provides antibodies that selectively bind to the14273 receptor protein and its variants and fragments. An antibody isconsidered to selectively bind, even if it also binds to other proteinsthat are not substantially homologous with the receptor protein. Theseother proteins share homology with a fragment or domain of the receptorprotein. This conservation in specific regions gives rise to antibodiesthat bind to both proteins by virtue of the homologous sequence. In thiscase, it would be understood that antibody binding to the receptorprotein is still selective. Preferred antibodies bind to receptormutants that are correlated with hypertrophy in myocytes, and correlatedwith cardiovascular disease.

To generate antibodies, an isolated receptor polypeptide is used as animmunogen to generate antibodies using standard techniques forpolyclonal and monoclonal antibody preparation. Either the full-lengthprotein or antigenic peptide fragment can be used. Regions having a highantigenicity index are shown in FIGS. 3 and 9.

Antibodies are preferably prepared from these regions or from discretefragments in these regions. However, antibodies can be prepared from anyregion of the peptide as described herein. A preferred fragment producesan antibody that diminishes or completely prevents ligand-binding.Antibodies can be developed against the entire receptor or portions ofthe receptor, for example, the intracellular carboxy terminal domain,the amino terminal extracellular domain, the entire transmembrane domainor specific segments, any of the intra or extracellular loops, or anyportions of the above. Antibodies may also be developed against specificfunctional sites, such as the site of ligand-binding, the site of Gprotein coupling, or sites that are glycosylated, phosphorylated,myristoylated, or amidated.

An antigenic fragment will typically comprise at least 6 contiguousamino acid residues. The antigenic peptide can comprise, however, atleast 12, at least 14 amino acid residues, at least 15 amino acidresidues, at least 20 amino acid residues, or at least 30 amino acidresidues. In one embodiment, fragments correspond to regions that arelocated on the surface of the protein, e.g., hydrophilic regions. Thesefragments are not to be construed, however, as encompassing anyfragments which may be disclosed prior to the invention.

Antibodies can be polyclonal or monoclonal. An intact antibody, or afragment thereof (e.g. Fab or F(ab′)₂) can be used.

Detection can be facilitated by coupling (i.e., physically linking) theantibody to a detectable substance. Examples of detectable substancesinclude various enzymes, prosthetic groups, fluorescent materials,luminescent materials, bioluminescent materials, and radioactivematerials. Examples of suitable enzymes include horseradish peroxidase,alkaline phosphatase, β-galactosidase, or acetylcholinesterase; examplesof suitable prosthetic group complexes include streptavidin/biotin andavidin/biotin; examples of suitable fluorescent materials includeumbelliferone, fluorescein, fluorescein isothiocyanate, rhodamine,dichlorotriazinylamine fluorescein, dansyl chloride or phycoerythrin; anexample of a luminescent material includes luminol; examples ofbioluminescent materials include luciferase, luciferin, and aequorin,and examples of suitable radioactive material include ¹²⁵I, ¹³¹I, ³⁵S or³H.

An appropriate immunogenic preparation can be derived from native,recombinantly expressed, protein or chemically synthesized peptides.

Antibody Uses

Since expression of the 14273 receptor has been correlated withcardiovascular disease, the uses of antibodies described belowpreferably apply to antibodies made from modified receptor proteinsderived from cells affected by the disease, which can be usedspecifically to treat or diagnose the disease. It is also understood,however, that antibodies can also be used to treat the disease where thereceptor is overexpressed, by binding to and inactivating overexpressedcopies of the receptor protein. This can be done by introducing theantibodies extracellularly or by means of “intrabodies”. Preferred cellsinclude, but are not limited to, myocytes, especially hypertrophiccardiac myocytes. Thus, in preferred embodiments, the antibody usesdescribed below preferably apply to tissues involved in heart disease.

The antibodies can be used to isolate a receptor protein by standardtechniques, such as affinity chromatography or immunoprecipitation. Inone embodiment, an antibody is prepared against a C-terminal antigenicsequence (SEQ ID NO:12, corresponds to amino acids 348-361 of SEQ IDNO:1), DTSVKRNDLSIISG. Accordingly, an antibody can be derived fromthese particular amino acids or from this approximate region. Theantibodies can facilitate the purification of the natural receptorprotein from cells and recombinantly produced receptor protein expressedin host cells.

The antibodies are useful to detect the presence of receptor protein incells or tissues to determine the pattern of expression of the receptoramong various tissues in an organism and over the course of normaldevelopment.

The antibodies can be used to detect receptor protein in situ, in vitro,or in a cell lysate or supernatant in order to evaluate the abundanceand pattern of expression.

The antibodies can be used to assess abnormal tissue distribution orabnormal expression during development.

Antibody detection of circulating fragments of the full length receptorprotein can be used to identify receptor turnover.

Further, the antibodies can be used to assess receptor expression indisease states, such as in active stages of the disease or in anindividual with a predisposition toward disease related to receptorfunction, such as cardiovascular disease. When a disorder is caused byan inappropriate tissue distribution, developmental expression, or levelof expression of the receptor protein, the antibody can be preparedagainst the normal receptor protein. If a disorder is characterized by aspecific mutation in the receptor protein, antibodies specific for thismutant protein can be used to assay for the presence of the specificmutant receptor protein. However, intracellularly-made antibodies(“intrabodies”) are also encompassed, which would recognizeintracellular receptor peptide regions.

The antibodies can also be used to assess normal and aberrantsubcellular localization of cells in the various tissues in an organism.Antibodies can be developed against the whole receptor or portions ofthe receptor, for example, portions of the amino terminal extracellulardomain or extracellular loops.

The diagnostic uses can be applied, not only in genetic testing, butalso in monitoring a treatment modality. Accordingly, where treatment isultimately aimed at correcting receptor expression level or the presenceof aberrant receptors and aberrant tissue distribution or developmentalexpression, antibodies directed against the receptor or relevantfragments can be used to monitor therapeutic efficacy.

Additionally, antibodies are useful in pharmacogenomic analysis. Thus,antibodies prepared against polymorphic receptor proteins can be used toidentify individuals that require modified treatment modalities.

The antibodies are also useful as diagnostic tools as an immunologicalmarker for aberrant receptor protein analyzed by electrophoreticmobility, isoelectric point, tryptic peptide digest, and other physicalassays known to those in the art.

The antibodies are also useful for tissue typing. Thus, where a specificreceptor protein has been correlated with expression in a specifictissue, antibodies that are specific for this receptor protein can beused to identify a tissue type.

The antibodies are also useful in forensic identification. Accordingly,where an individual has been correlated with a specific geneticpolymorphism resulting in a specific polymorphic protein, an antibodyspecific for the polymorphic protein can be used as an aid inidentification.

The antibodies are also useful for inhibiting receptor function, forexample, blocking ligand binding.

These uses can also be applied in a therapeutic context in whichtreatment involves inhibiting receptor function. An antibody can beused, for example, to block ligand binding. Antibodies can be preparedagainst specific fragments containing sites required for function oragainst intact receptor associated with a cell.

The invention also encompasses kits for using antibodies to detect thepresence of a receptor protein in a biological sample. The kit cancomprise antibodies such as a labeled or labelable antibody and acompound or agent for detecting receptor protein in a biological sample;means for determining the amount of receptor protein in the sample; andmeans for comparing the amount of receptor protein in the sample with astandard. The compound or agent can be packaged in a suitable container.The kit can further comprise instructions for using the kit to detectreceptor protein.

Polynucleotides

The nucleotide sequence in SEQ ID NO:2 and SEQ ID NO:5 was obtained bysequencing the deposited full length cDNA. Accordingly, the sequence ofthe deposited clone is controlling as to any discrepancies between thetwo and any reference to the sequence of SEQ ID NO:2 and SEQ ID NO:5includes reference to the sequence of the deposited cDNA.

The specifically disclosed cDNA comprises the coding region and 5′ and3′ untranslated sequences.

The human 14273 receptor cDNA is approximately 1743 nucleotides inlength and encodes a full length protein that is approximately 361 aminoacid residues in length. The nucleic acid is expressed in fetal brain,heart, skeletal muscle, thymus, prostate, placenta, and uterus.Structural analysis of the amino acid sequence of SEQ ID NO:1 and SEQ IDNO:4 is provided in FIGS. 3 and 9, a hydropathy plot. The figures showthe putative structure of the seven transmembrane segments, the aminoterminal extracellular domain and the carboxy terminal intracellulardomain.

As used herein, the term “transmembrane segment” refers to a structuralamino acid motif which includes a hydrophobic helix that spans theplasma membrane. The entire transmembrane domain spans from about aminoacid 46 to about amino acid 321 of SEQ ID NO:1 or SEQ ID NO:4.

Seven segments span the membrane and there are three intracellular andthree extracellular loops in this domain.

The invention provides isolated polynucleotides encoding a 14273receptor protein. The term “14273 polynucleotide” or “14273 nucleicacid” refers to the sequence shown in SEQ ID NO:2 and SEQ ID NO:5 or inthe deposited cDNA. The term “receptor polynucleotide” or “receptornucleic acid” further includes variants and fragments of the 14273polynucleotide.

An “isolated” receptor nucleic acid is one that is separated from othernucleic acid present in the natural source of the receptor nucleic acid.Preferably, an “isolated” nucleic acid is free of sequences whichnaturally flank the nucleic acid (i.e., sequences located at the 5′ and3′ ends of the nucleic acid) in the genomic DNA of the organism fromwhich the nucleic acid is derived. However, there can be some flankingnucleotide sequences, for example up to about 5 KB. The important pointis that the nucleic acid is isolated from flanking sequences such thatit can be subjected to the specific manipulations described herein suchas recombinant expression, preparation of probes and primers, and otheruses specific to the receptor nucleic acid sequences.

Moreover, an “isolated” nucleic acid molecule, such as a cDNA molecule,can be substantially free of other cellular material, or culture mediumwhen produced by recombinant techniques, or chemical precursors or otherchemicals when chemically synthesized. However, the nucleic acidmolecule can be fused to other coding or regulatory sequences and stillbe considered isolated.

For example, recombinant DNA molecules contained in a vector areconsidered isolated. Further examples of isolated DNA molecules includerecombinant DNA molecules maintained in heterologous host cells orpurified (partially or substantially) DNA molecules in solution.Isolated RNA molecules include in vivo or in vitro RNA transcripts ofthe isolated DNA molecules of the present invention. Isolated nucleicacid molecules according to the present invention further include suchmolecules produced synthetically.

The receptor polynucleotides can encode the mature protein plusadditional amino or carboxyl-terminal amino acids, or amino acidsinterior to the mature polypeptide (when the mature form has more thanone polypeptide chain, for instance). Such sequences may play a role inprocessing of a protein from precursor to a mature form, facilitateprotein trafficking, prolong or shorten protein half-life or facilitatemanipulation of a protein for assay or production, among other things.As generally is the case in situ, the additional amino acids may beprocessed away from the mature protein by cellular enzymes.

The receptor polynucleotides include, but are not limited to, thesequence encoding the mature polypeptide alone, the sequence encodingthe mature polypeptide and additional coding sequences, such as a leaderor secretory sequence (e.g., a pre-pro or pro-protein sequence), thesequence encoding the mature polypeptide, with or without the additionalcoding sequences, plus additional non-coding sequences, for exampleintrons and non-coding 5′ and 3′ sequences such as transcribed butnon-translated sequences that play a role in transcription, mRNAprocessing (including splicing and polyadenylation signals), ribosomebinding and stability of mRNA. In addition, the polynucleotide may befused to a marker sequence encoding, for example, a peptide thatfacilitates purification.

Receptor polynucleotides can be in the form of RNA, such as mRNA, or inthe form DNA, including cDNA and genomic DNA obtained by cloning orproduced by chemical synthetic techniques or by a combination thereof.The nucleic acid, especially DNA, can be double-stranded orsingle-stranded. Single-stranded nucleic acid can be the coding strand(sense strand) or the non-coding strand (anti-sense strand).

One receptor nucleic acid comprises the nucleotide sequence shown in SEQID NO:2, corresponding to human brain cDNA or the murine ortholog shownin SEQ ID NO:5.

In one embodiment, the receptor nucleic acid comprises only the codingregion.

The invention further provides variant receptor polynucleotides, andfragments thereof, that differ from the nucleotide sequence shown in SEQID NO:2 or SEQ ID NO:5 due to degeneracy of the genetic code and thusencode the same protein as that encoded by the nucleotide sequence shownin SEQ ID NO:2 or SEQ ID NO:5.

The invention also provides receptor nucleic acid molecules encoding thevariant polypeptides described herein. Such polynucleotides may benaturally occurring, such as allelic variants (same locus), homologs(different locus), and orthologs (different organism), or may beconstructed by recombinant DNA methods or by chemical synthesis. Suchnon-naturally occurring variants may be made by mutagenesis techniques,including those applied to polynucleotides, cells, or organisms.Accordingly, as discussed above, the variants can contain nucleotidesubstitutions, deletions, inversions and insertions.

Variation can occur in either or both the coding and non-coding regions.The variations can produce both conservative and non-conservative aminoacid substitutions.

Orthologs, homologs, and allelic variants can be identified usingmethods well known in the art. These variants comprise a nucleotidesequence encoding a receptor that is 50%, at least about 55%, typicallyat least about 70-75%, more typically at least about 80-85%, and mosttypically at least about 90-95% or more homologous to the nucleotidesequence shown in SEQ ID NO:2 or SEQ ID NO:5 or a fragment of thissequence. Such nucleic acid molecules can readily be identified as beingable to hybridize under stringent conditions, to the nucleotide sequenceshown in SEQ ID NO:2 or SEQ ID NO:5 or a fragment of the sequence. It isunderstood that stringent hybridization does not indicate substantialhomology where it is due to general homology, such as poly A sequences,or sequences common to all or most proteins, all GPCRs, or all family IGPCRs or sequences found dispersed throughout the genome that are notspecific to any genes, for example, homopolymer stretches. Moreover, itis understood that variants do not include any of the nucleic acidsequences that may have been disclosed prior to the invention. Preferredvariants include those that are correlated with hypertrophy of cardiacmyocytes and with congestive heart failure.

As used herein, the term “hybridizes under stringent conditions” isintended to describe conditions for hybridization and washing underwhich nucleotide sequences encoding a receptor at least 50%, 55%homologous to each other typically remain hybridized to each other. Theconditions can be such that sequences at least about 65%, at least about70%, or at least about 75% or more homologous to each other typicallyremain hybridized to each other. Such stringent conditions are known tothose skilled in the art and can be found in Current Protocols inMolecular Biology, John Wiley & Sons, N.Y. (1989), 6.3.1-6.3.6. Oneexample of stringent hybridization conditions are hybridization in 6×sodium chloride/sodium citrate (SSC) at about 45° C., followed by one ormore washes in 0.2×SSC, 0.1% SDS at 50-65° C. In one embodiment, anisolated receptor nucleic acid molecule that hybridizes under stringentconditions to the sequence of SEQ ID NO:2 corresponds to anaturally-occurring nucleic acid molecule. As used herein, a“naturally-occurring” nucleic acid molecule refers to an RNA or DNAmolecule having a nucleotide sequence that occurs in nature (e.g.,encodes a natural protein).

Furthermore, the invention provides polynucleotides that comprise afragment of the full length receptor polynucleotides. The fragment canbe single or double stranded and can comprise DNA or RNA. The fragmentcan be derived from either the coding or the non-coding sequence.

In one embodiment, an isolated receptor nucleic acid fragment is atleast 5 nucleotides in length and is derived from the sequence from1-410, 118-1295, or 1630-1743 nucleotides in length and hybridizes understringent conditions to the nucleotide molecule comprising thenucleotide sequence of SEQ ID NO:2 or SEQ ID NO:5. In other embodiments,the nucleic acid is at least 10, 15, 20, 30, 40, 50, 100, 250, or 500nucleotides in length or greater.

In another embodiment, the fragment comprises contiguous nucleotidesfrom around 410 to around 442 of SEQ ID NO:2 or SEQ ID NO:5 that aregreater than 13, 442-473 of SEQ ID NO:2 or SEQ ID NO:5 that are greaterthan 26, 605-745 of SEQ ID NO:2 or SEQ ID NO:5 that are greater than 44,745-857 of SEQ ID NO:2 or SEQ ID NO:5 that are greater than 17, 857-924of SEQ ID NO:2 or SEQ ID NO:5 that are greater than 23, 925-1118 of SEQID NO:2 or SEQ ID NO:5 that are greater than 23, and 1295-1630 of SEQ IDNO:2 or SEQ ID NO:5 that are greater than 25.

In another embodiment an isolated receptor nucleic acid encodes theentire coding region from amino acid 1 to amino acid 321 of SEQ ID NO:1or SEQ ID NO:4. In another embodiment the isolated receptor nucleic acidencodes a sequence corresponding to the mature protein from about aminoacid 36 to amino acid 321 of SEQ ID NO:1 or SEQ ID NO:4. Other fragmentsinclude nucleotide sequences that include part, or all, of the codingregion and extend into either the 5′ or 3′ noncoding region, or both ofthese regions. Other fragments include nucleotide sequences encoding theamino acid fragments described herein. Further fragments can includesubfragments of the specific domains or sites described herein.Fragments also include nucleic acid sequences corresponding to specificamino acid sequences described above or fragments thereof. Nucleic acidfragments, according to the present invention, are not to be construedas encompassing those fragments that may have been disclosed prior tothe invention.

Receptor nucleic acid fragments further include sequences correspondingto the domains described herein, subregions also described, and specificfunctional sites. Receptor nucleic acid fragments also includecombinations of the domains, segments, loops, and other functional sitesdescribed above. Thus, for example, a receptor nucleic acid couldinclude sequences corresponding to the amino terminal extracellulardomain and one transmembrane fragment. A person of ordinary skill in theart would be aware of the many permutations that are possible.

However, it is understood that a receptor fragment includes any nucleicacid sequence that does not include the entire gene.

Receptor nucleic acid fragments include nucleic acid molecules encodinga polypeptide comprising the amino terminal extracellular domainincluding amino acid residues from 1 to about 45 of SEQ ID NO:1 or SEQID NO:4, a polypeptide comprising the region spanning the transmembranedomain (amino acid residues from about 46 to about 321 of SEQ ID NO:1 orSEQ ID NO:4), a polypeptide comprising the carboxy terminalintracellular domain (amino acid residues from about 322 to about 361 ofSEQ ID NO:1 or SEQ ID NO:4), and a polypeptide encoding the G-proteinreceptor signature (135-136 or surrounding amino acid residues fromabout 125 to about 145 of SEQ ID NO:1 or SEQ ID NO:4), nucleic acidmolecules encoding any of the seven transmembrane segments,extracellular or intracellular loops, glycosylation, phosphorylation,myristoylation, and amidation sites. Where the location of the domainshave been predicted by computer analysis, one of ordinary skill wouldappreciate that the amino acid residues constituting these domains canvary depending on the criteria used to define the domains.

The invention also provides receptor nucleic acid fragments that encodeepitope bearing regions of the receptor proteins described herein.

The isolated receptor polynucleotide sequences, and especiallyfragments, are useful as DNA probes and primers.

For example, the coding region of a receptor gene can be isolated usingthe known nucleotide sequence to synthesize an oligonucleotide probe. Alabeled probe can then be used to screen a cDNA library, genomic DNAlibrary, or mRNA to isolate nucleic acid corresponding to the codingregion. Further, primers can be used in PCR reactions to clone specificregions of receptor genes.

A probe/primer typically comprises substantially purifiedoligonucleotide. The oligonucleotide typically comprises a region ofnucleotide sequence that hybridizes under stringent conditions to atleast about 10, 12, typically about 25, more typically about 40, 50 or75 consecutive nucleotides of SEQ ID NO:2 or SEQ ID NO:5 sense oranti-sense strand or other receptor polynucleotides. A probe furthercomprises a label, e.g., radioisotope, fluorescent compound, enzyme, orenzyme co-factor.

Polynucleotide Uses

Since zexpression of the 14273 receptor has been associated withcardiovascular disease, the polynucleotides described herein can be usedfor treatment and diagnosis of patients having, or predisposed tohaving, cardiovascular disease, including, but not limited to,congestive heart failure. The induction of receptor mRNA has beendemonstrated by the inventors to occur in hypertrophic human cardiacmyocytes, the induction being associated with morphological change.Accordingly, a preferred use of the polypeptides is for treatment anddiagnosis of cardiovascular disease in which cardiomyocyte hypertrophyis involved. Such cardiovascular disease/disorders include, but are notlimited to, dilation, ischemia, cardiac fibrosis, fibro-elastosis,general loss of cardiac muscle tone, and thrombosis.

The receptor polynucleotides are useful for probes, primers, and inbiological assays. Where the polynucleotides are used to assess GPCRproperties or functions, such as in the assays described herein, all orless than all of the entire cDNA can be useful. In this case, evenfragments that may have been known prior to the invention areencompassed. Thus, for example, assays specifically directed to GPCRfunctions, such as assessing agonist or antagonist activity, encompassthe use of known fragments. Further, diagnostic methods for assessingreceptor function can also be practiced with any fragment, includingthose fragments that may have been known prior to the invention.Similarly, in methods involving treatment of receptor dysfunction, allfragments are encompassed, including those which may have been known inthe art.

The receptor polynucleotides are useful as a hybridization probe forcDNA and genomic DNA to isolate a full-length cDNA and genomic clonesencoding the polypeptide described in SEQ ID NO:1 or SEQ ID NO:4 and toisolate cDNA and genomic clones that correspond to variants producingthe same polypeptide shown in SEQ ID NO:1 or SEQ ID NO:4 or the othervariants described herein. Variants can be isolated from the same tissueand organism from which the polypeptide shown in SEQ ID NO:1 or SEQ IDNO:4 was isolated, different tissues from the same organism, or fromdifferent organisms. This method is useful for isolating genes and cDNAthat are developmentally-controlled and therefore may be expressed inthe same tissue or different tissues at different points in thedevelopment of an organism.

The probe can correspond to any sequence along the entire length of thegene encoding the receptor. Accordingly, it could be derived from 5′noncoding regions, the coding region, and 3′ noncoding regions. It isunderstood, however, that the probe would not encompass a fragmentalready described prior to the invention.

The nucleic acid probe can be, for example, the full-length cDNA of SEQID NO:1 or SEQ ID NO:4, or a fragment thereof, such as anoligonucleotide of at least 10, 12, 15, 30, 50, 100, 250 or 500nucleotides in length and sufficient to specifically hybridize understringent conditions to mRNA or DNA.

Fragments of the polynucleotides described herein are also useful tosynthesize larger fragments or full-length polynucleotides describedherein. For example, a fragment can be hybridized to any portion of anmRNA and a larger or full-length cDNA can be produced.

The fragments are also useful to synthesize antisense molecules ofdesired length and sequence.

The receptor polynucleotides are also useful as primers for PCR toamplify any given region of a receptor polynucleotide.

The receptor polynucleotides are also useful for constructingrecombinant vectors. Such vectors include expression vectors thatexpress a portion of, or all of, the receptor polypeptides. Vectors alsoinclude insertion vectors, used to integrate into another polynucleotidesequence, such as into the cellular genome, to alter in situ expressionof receptor genes and gene products. For example, an endogenous receptorcoding sequence can be replaced via homologous recombination with all orpart of the coding region containing one or more specifically introducedmutations.

The receptor polynucleotides are also useful for expressing antigenicportions of the receptor proteins.

The receptor polynucleotides are also useful as probes for determiningthe chromosomal positions of the receptor polynucleotides by means of insitu hybridization methods.

The receptor polynucleotide probes are also useful to determine patternsof the presence of the gene encoding the receptors and their variantswith respect to tissue distribution, for example, whether geneduplication has occurred and whether the duplication occurs in all oronly a subset of tissues. The genes can be naturally-occurring or canhave been introduced into a cell, tissue, or organism exogenously.

The receptor polynucleotides are also useful for designing ribozymescorresponding to all, or a part, of the mRNA produced from genesencoding the polynucleotides described herein.

The receptor polynucleotides are also useful for constructing host cellsexpressing a part, or all, of the receptor polynucleotides andpolypeptides.

The receptor polynucleotides are also useful for constructing transgenicanimals expressing all, or a part, of the receptor polynucleotides andpolypeptides. These animals are useful as model systems for GPCR-relateddisorders, such as congestive heart failure. Such animal models ofcardiovascular diseases can then be used to test compounds for theireffect, through the receptor gene or gene product, on the development orprogression of the disease.

The receptor polynucleotides are also useful for making vectors thatexpress part, or all, of the receptor polypeptides.

The receptor polynucleotides are also useful as hybridization probes fordetermining the level of receptor nucleic acid expression. Accordingly,the probes can be used to detect the presence of, or to determine levelsof, receptor nucleic acid in cells, tissues, and in organisms. Thenucleic acid whose level is determined can be DNA or RNA. Accordingly,probes corresponding to the polypeptides described herein can be used toassess gene copy number in a given cell, tissue, or organism. This isparticularly relevant in cases in which there has been an amplificationof the receptor genes.

Alternatively, the probe can be used in an in situ hybridization contextto assess the position of extra copies of the receptor genes, as onextrachromosomal elements or as integrated into chromosomes in which thereceptor gene is not normally found, for example as a homogeneouslystaining region.

These uses are relevant for diagnosis of disorders involving an increaseor decrease in receptor expression relative to normal results.

In vitro techniques for detection of mRNA include Northernhybridizations and in situ hybridizations. In vitro techniques fordetecting DNA includes Southern hybridizations and in situhybridization.

Probes can be used as a part of a diagnostic test kit for identifyingcells or tissues that express a receptor protein, such as by measuring alevel of a receptor-encoding nucleic acid in a sample of cells from asubject e.g., mRNA or genomic DNA, or determining if a receptor gene hasbeen mutated.

Nucleic acid expression assays are useful for drug screening to identifycompounds that modulate receptor nucleic acid expression.

The invention thus provides a method for identifying a compound that canbe used to treat a disorder associated with nucleic acid expression ofthe receptor gene. The method typically includes assaying the ability ofthe compound to modulate the expression of the receptor nucleic acid andthus identifying a compound that can be used to treat a disordercharacterized by undesired receptor nucleic acid expression.

The assays can be performed in cell-based and cell-free systems.Cell-based assays include cells naturally expressing the receptornucleic acid or recombinant cells genetically engineered to expressspecific nucleic acid sequences.

Alternatively, candidate compounds can be assayed in vivo in patients orin transgenic animals. Thus, variant receptor nucleic acid that resultsin an increase in the level or a change in the nucleotide sequence canbe introduced into a transgenic animal to serve as the target for acandidate compound. The mutation may be naturally-occurring or may becreated in the laboratory.

The assay for receptor nucleic acid expression can involve direct assayof nucleic acid levels, such as mRNA levels, or on collateral compoundsinvolved in the signal pathway (such as cyclic AMP orphosphatidylinositol turnover). Further, the expression of genes thatare up- or down-regulated in response to the receptor protein signalpathway can also be assayed. In this embodiment the regulatory regionsof these genes can be operably linked to a reporter gene such asluciferase.

Thus, modulators of receptor gene expression can be identified in amethod wherein a cell is contacted with a candidate compound and theexpression of mRNA determined. The level of expression of receptor mRNAin the presence of the candidate compound is compared to the level ofexpression of receptor mRNA in the absence of the candidate compound.The candidate compound can then be identified as a modulator of nucleicacid expression based on this comparison and be used, for example totreat a disorder characterized by aberrant nucleic acid expression. Whenexpression of mRNA is statistically significantly greater in thepresence of the candidate compound than in its absence, the candidatecompound is identified as a stimulator of nucleic acid expression. Whennucleic acid expression is statistically significantly less in thepresence of the candidate compound than in its absence, the candidatecompound is identified as an inhibitor of nucleic acid expression.

Accordingly, the invention provides methods of treatment, with thenucleic acid as a target, using a compound identified through drugscreening as a gene modulator to modulate receptor nucleic acidexpression. Modulation includes both up-regulation (i.e. activation oragonization) or down-regulation (suppression or antagonization) ornucleic acid expression.

Alternatively, a modulator for receptor nucleic acid expression can be asmall molecule or drug identified using the screening assays describedherein as long as the drug or small molecule inhibits the receptornucleic acid expression.

The receptor polynucleotides are also useful for monitoring theeffectiveness of modulating compounds on the expression or activity ofthe receptor gene in clinical trials or in a treatment regimen. Thus,the gene expression pattern can serve as a barometer for the continuingeffectiveness of treatment with the compound, particularly withcompounds to which a patient can develop resistance. The gene expressionpattern can also serve as a marker indicative of a physiologicalresponse of the affected cells to the compound. Accordingly, suchmonitoring would allow either increased administration of the compoundor the administration of alternative compounds to which the patient hasnot become resistant. Similarly, if the level of nucleic acid expressionfalls below a desirable level, administration of the compound could becommensurately decreased.

The receptor polynucleotides are also useful in diagnostic assays forqualitative changes in receptor nucleic acid, and particularly inqualitative changes that lead to pathology. The polynucleotides can beused to detect mutations in receptor genes and gene expression productssuch as mRNA. The polynucleotides can be used as hybridization probes todetect naturally-occurring genetic mutations in the receptor gene andthereby to determine whether a subject with the mutation is at risk fora disorder caused by the mutation. Mutations include deletion, addition,or substitution of one or more nucleotides in the gene, chromosomalrearrangement, such as inversion or transposition, modification ofgenomic DNA, such as aberrant methylation patterns or changes in genecopy number, such as amplification. Detection of a mutated form of thereceptor gene associated with a dysfunction provides a diagnostic toolfor an active disease or susceptibility to disease when the diseaseresults from overexpression, underexpression, or altered expression of areceptor protein.

Individuals carrying mutations in the receptor gene can be detected atthe nucleic acid level by a variety of techniques. Genomic DNA can beanalyzed directly or can be amplified by using PCR prior to analysis.RNA or cDNA can be used in the same way.

In certain embodiments, detection of the mutation involves the use of aprobe/primer in a polymerase chain reaction (PCR) (see, e.g. U.S. Pat.Nos. 4,683,195 and 4,683,202), such as anchor PCR or RACE PCR, or,alternatively, in a ligation chain reaction (LCR) (see, e.g., Landegranet al., Science 241:1077-1080 (1988); and Nakazawa et al., PNAS91:360-364 (1994)), the latter of which can be particularly useful fordetecting point mutations in the gene (see Abravaya et al., NucleicAcids Res. 23:675-682 (1995)). This method can include the steps ofcollecting a sample of cells from a patient, isolating nucleic acid(e.g., genomic, mRNA or both) from the cells of the sample, contactingthe nucleic acid sample with one or more primers which specificallyhybridize to a gene under conditions such that hybridization andamplification of the gene (if present) occurs, and detecting thepresence or absence of an amplification product, or detecting the sizeof the amplification product and comparing the length to a controlsample. Deletions and insertions can be detected by a change in size ofthe amplified product compared to the normal genotype. Point mutationscan be identified by hybridizing amplified DNA to normal RNA orantisense DNA sequences.

Alternatively, mutations in a receptor gene can be directly identified,for example, by alterations in restriction enzyme digestion patternsdetermined by gel electrophoresis.

Further, sequence-specific ribozymes (U.S. Pat. No. 5,498,531) can beused to score for the presence of specific mutations by development orloss of a ribozyme cleavage site.

Perfectly matched sequences can be distinguished from mismatchedsequences by nuclease cleavage digestion assays or by differences inmelting temperature.

Sequence changes at specific locations can also be assessed by nucleaseprotection assays such as RNase and S1 protection or the chemicalcleavage method.

Furthermore, sequence differences between a mutant receptor gene and awild-type gene can be determined by direct DNA sequencing. A variety ofautomated sequencing procedures can be utilized when performing thediagnostic assays ((1995) Biotechniques 19:448), including sequencing bymass spectrometry (see, e.g., PCT International Publication No. WO94/16101; Cohen et al., Adv. Chromatogr. 36:127-162 (1996); and Griffinet al., Appl. Biochem. Biotechnol. 38:147-159 (1993)).

Other methods for detecting mutations in the gene include methods inwhich protection from cleavage agents is used to detect mismatched basesin RNA/RNA or RNA/DNA duplexes (Myers et al., Science 230:1242 (1985));Cotton et al., PNAS 85:4397 (1988); Saleeba et al., Meth. Enzymol.217:286-295 (1992)), electrophoretic mobility of mutant and wild typenucleic acid is compared (Orita et al., PNAS 86:2766 (1989); Cotton etal., Mutat. Res. 285:125-144 (1993); and Hayashi et al., Genet. Anal.Tech. Appl. 9:73-79 (1992)), and movement of mutant or wild-typefragments in polyacrylamide gels containing a gradient of denaturant isassayed using denaturing gradient gel electrophoresis (Myers et al.,Nature 313:495 (1985)). Examples of other techniques for detecting pointmutations include selective oligonucleotide hybridization, selectiveamplification, and selective primer extension.

The receptor polynucleotides are also useful for testing an individualfor a genotype that while not necessarily causing the disease,nevertheless affects the treatment modality. Thus, the polynucleotidescan be used to study the relationship between an individual's genotypeand the individual's response to a compound used for treatment(pharmacogenomic relationship). In the present case, for example, amutation in the receptor gene that results in altered affinity forligand could result in an excessive or decreased drug effect withstandard concentrations of ligand that activates the receptor.Accordingly, the receptor polynucleotides described herein can be usedto assess the mutation content of the receptor gene in an individual inorder to select an appropriate compound or dosage regimen for treatment.

Thus polynucleotides displaying genetic variations that affect treatmentprovide a diagnostic target that can be used to tailor treatment in anindividual. Accordingly, the production of recombinant cells and animalscontaining these polymorphisms allow effective clinical design oftreatment compounds and dosage regimens.

The receptor polynucleotides are also useful for chromosomeidentification when the sequence is identified with an individualchromosome and to a particular location on the chromosome. First, theDNA sequence is matched to the chromosome by in situ or otherchromosome-specific hybridization. Sequences can also be correlated tospecific chromosomes by preparing PCR primers that can be used for PCRscreening of somatic cell hybrids containing individual chromosomes fromthe desired species. Only hybrids containing the chromosome containingthe gene homologous to the primer will yield an amplified fragment.Sublocalization can be achieved using chromosomal fragments. Otherstrategies include prescreening with labeled flow-sorted chromosomes andpreselection by hybridization to chromosome-specific libraries. Furthermapping strategies include fluorescence in situ hybridization whichallows hybridization with probes shorter than those traditionally used.Reagents for chromosome mapping can be used individually to mark asingle chromosome or a single site on the chromosome, or panels ofreagents can be used for marking multiple sites and/or multiplechromosomes. Reagents corresponding to noncoding regions of the genesactually are preferred for mapping purposes. Coding sequences are morelikely to be conserved within gene families, thus increasing the chanceof cross hybridizations during chromosomal mapping.

The receptor polynucleotides can also be used to identify individualsfrom small biological samples. This can be done for example usingrestriction fragment-length polymorphism (RFLP) to identify anindividual. Thus, the polynucleotides described herein are useful as DNAmarkers for RFLP (See U.S. Pat. No. 5,272,057).

Furthermore, the receptor sequence can be used to provide an alternativetechnique which determines the actual DNA sequence of selected fragmentsin the genome of an individual. Thus, the receptor sequences describedherein can be used to prepare two PCR primers from the 5′ and 3′ ends ofthe sequences. These primers can then be used to amplify DNA from anindividual for subsequent sequencing.

Panels of corresponding DNA sequences from individuals prepared in thismanner can provide unique individual identifications, as each individualwill have a unique set of such DNA sequences. It is estimated thatallelic variation in humans occurs with a frequency of about once pereach 500 bases. Allelic variation occurs to some degree in the codingregions of these sequences, and to a greater degree in the noncodingregions. The receptor sequences can be used to obtain suchidentification sequences from individuals and from tissue. The sequencesrepresent unique fragments of the human genome. Each of the sequencesdescribed herein can, to some degree, be used as a standard againstwhich DNA from an individual can be compared for identificationpurposes.

If a panel of reagents from the sequences is used to generate a uniqueidentification database for an individual, those same reagents can laterbe used to identify tissue from that individual. Using the uniqueidentification database, positive identification of the individual,living or dead, can be made from extremely small tissue samples.

The receptor polynucleotides can also be used in forensic identificationprocedures. PCR technology can be used to amplify DNA sequences takenfrom very small biological samples, such as a single hair follicle, bodyfluids (e.g. blood, saliva, or semen). The amplified sequence can thenbe compared to a standard allowing identification of the origin of thesample.

The receptor polynucleotides can thus be used to provide polynucleotidereagents, e.g., PCR primers, targeted to specific loci in the humangenome, which can enhance the reliability of DNA-based forensicidentifications by, for example, providing another “identificationmarker” (i.e. another DNA sequence that is unique to a particularindividual). As described above, actual base sequence information can beused for identification as an accurate alternative to patterns formed byrestriction enzyme generated fragments. Sequences targeted to thenoncoding region are particularly useful since greater polymorphismoccurs in the noncoding regions, making it easier to differentiateindividuals using this technique. Fragments are at least 10 bases.

The receptor polynucleotides can further be used to providepolynucleotide reagents, e.g., labeled or labelable probes which can beused in, for example, an in situ hybridization technique, to identify aspecific tissue. This is useful in cases in which a forensic pathologistis presented with a tissue of unknown origin. Panels of receptor probescan be used to identify tissue by species and/or by organ type.

In a similar fashion, these primers and probes can be used to screentissue culture for contamination (i.e. screen for the presence of amixture of different types of cells in a culture).

Alternatively, the receptor polynucleotides can be used directly toblock transcription or translation of receptor gene sequences by meansof antisense or ribozyme constructs. Thus, in a disorder characterizedby abnormally high or undesirable receptor gene expression, as is thecase for cardiovascular disease associated with cardiomyocytehypertrophy, nucleic acids can be directly used for treatment.

The receptor polynucleotides are thus useful as antisense constructs tocontrol receptor gene expression in cells, tissues, and organisms. A DNAantisense polynucleotide is designed to be complementary to a region ofthe gene involved in transcription, preventing transcription and henceproduction of receptor protein. An antisense RNA or DNA polynucleotidewould hybridize to the mRNA and thus block translation of mRNA intoreceptor protein.

Examples of antisense molecules useful to inhibit nucleic acidexpression include antisense molecules complementary to a fragment ofthe 5′ untranslated region of SEQ ID NO:2 or SEQ ID NO:5 which alsoincludes the start codon and antisense molecules which are complementaryto a fragment of the 3′ untranslated region of SEQ ID NO:2 or SEQ IDNO:5.

Alternatively, a class of antisense molecules can be used to inactivatemRNA in order to decrease expression of receptor nucleic acid.Accordingly, these molecules can treat a disorder characterized byabnormal or undesired receptor nucleic acid expression. This techniqueinvolves cleavage by means of ribozymes containing nucleotide sequencescomplementary to one or more regions in the mRNA that attenuate theability of the mRNA to be translated. Possible regions include codingregions and particularly coding regions corresponding to the catalyticand other functional activities of the receptor protein, such as ligandbinding.

The receptor polynucleotides also provide vectors for gene therapy inpatients containing cells that are aberrant in receptor gene expression.Thus, recombinant cells, which include the patient's cells that havebeen engineered ex vivo and returned to the patient, are introduced intoan individual where the cells produce the desired receptor protein totreat the individual.

The invention also encompasses kits for detecting the presence of areceptor nucleic acid in a biological sample. For example, the kit cancomprise reagents such as a labeled or labelable nucleic acid or agentcapable of detecting receptor nucleic acid in a biological sample; meansfor determining the amount of receptor nucleic acid in the sample; andmeans for comparing the amount of receptor nucleic acid in the samplewith a standard. The compound or agent can be packaged in a suitablecontainer. The kit can further comprise instructions for using the kitto detect receptor mRNA or DNA.

Vectors/Host Cells

The invention also provides vectors containing the receptorpolynucleotides. The term “vector” refers to a vehicle, preferably anucleic acid molecule, that can transport the receptor polynucleotides.When the vector is a nucleic acid molecule, the receptor polynucleotidesare covalently linked to the vector nucleic acid. With this aspect ofthe invention, the vector includes a plasmid, single or double strandedphage, a single or double stranded RNA or DNA viral vector, orartificial chromosome, such as a BAC, PAC, YAC, OR MAC.

A vector can be maintained in the host cell as an extrachromosomalelement where it replicates and produces additional copies of thereceptor polynucleotides. Alternatively, the vector may integrate intothe host cell genome and produce additional copies of the receptorpolynucleotides when the host cell replicates.

The invention provides vectors for the maintenance (cloning vectors) orvectors for expression (expression vectors) of the receptorpolynucleotides. The vectors can function in prokaryotic or eukaryoticcells or in both (shuttle vectors).

Expression vectors contain cis-acting regulatory regions that areoperably linked in the vector to the receptor polynucleotides such thattranscription of the polynucleotides is allowed in a host cell. Thepolynucleotides can be introduced into the host cell with a separatepolynucleotide capable of affecting transcription. Thus, the secondpolynucleotide may provide a trans-acting factor interacting with thecis-regulatory control region to allow transcription of the receptorpolynucleotides from the vector. Alternatively, a trans-acting factormay be supplied by the host cell. Finally, a trans-acting factor can beproduced from the vector itself.

It is understood, however, that in some embodiments, transcriptionand/or translation of the receptor polynucleotides can occur in acell-free system.

The regulatory sequence to which the polynucleotides described hereincan be operably linked include promoters for directing mRNAtranscription. These include, but are not limited to, the left promoterfrom bacteriophage λ, the lac, TRP, and TAC promoters from E. coli, theearly and late promoters from SV40, the CMV immediate early promoter,the adenovirus early and late promoters, and retrovirus long-terminalrepeats.

In addition to control regions that promote transcription, expressionvectors may also include regions that modulate transcription, such asrepressor binding sites and enhancers. Examples include the SV40enhancer, the cytomegalovirus immediate early enhancer, polyomaenhancer, adenovirus enhancers, and retrovirus LTR enhancers.

In addition to containing sites for transcription initiation andcontrol, expression vectors can also contain sequences necessary fortranscription termination and, in the transcribed region a ribosomebinding site for translation. Other regulatory control elements forexpression include initiation and termination codons as well aspolyadenylation signals. The person of ordinary skill in the art wouldbe aware of the numerous regulatory sequences that are useful inexpression vectors. Such regulatory sequences are described, forexample, in Sambrook et al., Molecular Cloning: A Laboratory Manual.2^(nd) . ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor,N.Y., (1989).

A variety of expression vectors can be used to express a receptorpolynucleotide. Such vectors include chromosomal, episomal, andvirus-derived vectors, for example vectors derived from bacterialplasmids, from bacteriophage, from yeast episomes, from yeastchromosomal elements, including yeast artificial chromosomes, fromviruses such as baculoviruses, papovaviruses such as SV40, Vacciniaviruses, adenoviruses, poxviruses, pseudorabies viruses, andretroviruses. Vectors may also be derived from combinations of thesesources such as those derived from plasmid and bacteriophage geneticelements, e.g. cosmids and phagemids. Appropriate cloning and expressionvectors for prokaryotic and eukaryotic hosts are described in Sambrooket al., Molecular Cloning: A Laboratory Manual. 2^(nd) . ed., ColdSpring Harbor Laboratory Press, Cold Spring Harbor, N.Y., (1989).

The regulatory sequence may provide constitutive expression in one ormore host cells (i.e. tissue specific) or may provide for inducibleexpression in one or more cell types such as by temperature, nutrientadditive, or exogenous factor such as a hormone or other ligand. Avariety of vectors providing for constitutive and inducible expressionin prokaryotic and eukaryotic hosts are well known to those of ordinaryskill in the art.

In one specifically disclosed embodiment, expression of the receptorgene is under control of the alpha-MHC promoter, that allows specificexpression in cardiomyocytes. This promoter could be further modified sothat it is specifically inducible in cardiomyocytes while also beingspecifically expressed in these cells.

The receptor polynucleotides can be inserted into the vector nucleicacid by well-known methodology. Generally, the DNA sequence that willultimately be expressed is joined to an expression vector by cleavingthe DNA sequence and the expression vector with one or more restrictionenzymes and then ligating the fragments together. Procedures forrestriction enzyme digestion and ligation are well known to those ofordinary skill in the art.

The vector containing the appropriate polynucleotide can be introducedinto an appropriate host cell for propagation or expression usingwell-known techniques. Bacterial cells include, but are not limited to,E. coli, Streptomyces, and Salmonella typhimurium. Eukaryotic cellsinclude, but are not limited to, yeast, insect cells such as Drosophila,animal cells such as COS, HEK 293, and CHO cells, and plant cells. It isunderstood that any of the established cell lines or any cell capable ofbeing established are useful for producing long-term recombinantexpression of the receptor polynucleotides. However, in someembodiments, it is useful to obtain recombinant expression innon-established cells as well.

As described herein, it may be desirable to express the polypeptide as afusion protein. Accordingly, the invention provides fusion vectors thatallow for the production of the receptor polypeptides. Fusion vectorscan increase the expression of a recombinant protein, increase thesolubility of the recombinant protein, and aid in the purification ofthe protein by acting for example as a ligand for affinity purification.A proteolytic cleavage site may be introduced at the junction of thefusion moiety so that the desired polypeptide can ultimately beseparated from the fusion moiety. Proteolytic enzymes include, but arenot limited to, factor Xa, thrombin, and enterokinase. Typical fusionexpression vectors include pGEX (Smith et al., Gene 67:3140 (1988)),pMAL (New England Biolabs, Beverly, Mass.) and pRIT5 (Pharmacia,Piscataway, N.J.) which fuse glutathione S-transferase (GST), maltose Ebinding protein, or protein A, respectively, to the target recombinantprotein. Examples of suitable inducible non-fusion E. coli expressionvectors include pTrc (Amann et al., Gene 69:301-315 (1988)) and pET 11d(Studier et al., Gene Expression Technology: Methods in Enzymology185:60-89 (1990)).

Recombinant protein expression can be maximized in a host bacteria byproviding a genetic background wherein the host cell has an impairedcapacity to proteolytically cleave the recombinant protein. (Gottesman,S., Gene Expression Technology: Methods in Enzymology 185, AcademicPress, San Diego, Calif. (1990) 119-128). Alternatively, the sequence ofthe polynucleotide of interest can be altered to provide preferentialcodon usage for a specific host cell, for example E. coli. (Wada et al.,Nucleic Acids Res. 20:2111-2118 (1992)).

The receptor polynucleotides can also be expressed by expression vectorsthat are operative in yeast. Examples of vectors for expression in yeaste.g., S. cerevisiae include pYepSec1 (Baldari, et al., EMBO J. 6:229-234(1987)), pMFa (Kurjan et al., Cell 30:933-943(1982)), pJRY88 (Schultz etal., Gene 54:113-123 (1987)), and pYES2 (Invitrogen Corporation, SanDiego, Calif.).

The receptor polynucleotides can also be expressed in insect cellsusing, for example, baculovirus expression vectors. Baculovirus vectorsavailable for expression of proteins in cultured insect cells (e.g., Sf9 cells) include the pAc series (Smith et al., Mol. Cell Biol.3:2156-2165 (1983)) and the pVL series (Lucklow et al., Virology170:31-39 (1989)).

In certain embodiments of the invention, the polynucleotides describedherein are expressed in mammalian cells using mammalian expressionvectors. Examples of mammalian expression vectors include pCDM8 (Seed,B. Nature 329:840(1987)) and pMT2PC (Kaufman et al., EMBO J. 6:187-195(1987)).

The expression vectors listed herein are provided by way of example onlyof the well-known vectors available to those of ordinary skill in theart that would be useful to express the receptor polynucleotides. Theperson of ordinary skill in the art would be aware of other vectorssuitable for maintenance propagation or expression of thepolynucleotides described herein. These are found for example inSambrook, J., Fritsh, E. F., and Maniatis, T. Molecular Cloning: ALaboratory Manual. 2^(nd) , ed., Cold Spring Harbor Laboratory, ColdSpring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1989.

The invention also encompasses vectors in which the nucleic acidsequences described herein are cloned into the vector in reverseorientation, but operably linked to a regulatory sequence that permitstranscription of antisense RNA. Thus, an antisense transcript can beproduced to all, or to a portion, of the polynucleotide sequencesdescribed herein, including both coding and non-coding regions.Expression of this antisense RNA is subject to each of the parametersdescribed above in relation to expression of the sense RNA (regulatorysequences, constitutive or inducible expression, tissue-specificexpression).

The invention also relates to recombinant host cells containing thevectors described herein. Host cells therefore include prokaryoticcells, lower eukaryotic cells such as yeast, other eukaryotic cells suchas insect cells, and higher eukaryotic cells such as mammalian cells.

In a preferred embodiment, recombinant cells are cardiac myocytes. Thesecan be derived from humans or other animals having or predisposed tohaving a cardiovascular disease involving hypertrophy of cardiomyocytes.The cardiomyocytes thus can be phenotypically normal or pathological,including at various stages of hypertrophy. Such recombinant cells canbe derived from transgenic animals or can be made, used, and derivedfrom in vitro cell culture. Further, cardiomyocytes can be normal butconstructed to contain vectors that overexpress receptor RNA or proteinor express variant receptor RNA or protein.

Mammalian cells include cellular test systems for ascertaining theeffects of a given mutation on cell function, the function of a givenmutation, the testing of compounds for the effect on a cell containing agiven mutation, creating recombinant cells ex vivo for introduction intoa subject, such as a transgenic animal or affected patient. In oneembodiment, cells are derived from subjects or tissues known to beinvolved in cardiovascular disease or in the development ofcardiovascular disease. Cells include, but are not limited to, cardiacmyocytes and especially hypertrophic cardiac myocytes, other cells ofthe heart, cells from skeletal muscle, thymus, uterus, and prostate. Inaddition, cells appropriate for test systems can include fetal brain andplacenta, as well as established cell lines, such as COS, HEK-293, andCHO cells.

The recombinant host cells are prepared by introducing the vectorconstructs described herein into the cells by techniques readilyavailable to the person of ordinary skill in the art. These include, butare not limited to, calcium phosphate transfection,DEAE-dextran-mediated transfection, cationic lipid-mediatedtransfection, electroporation, transduction, infection, lipofection, andother techniques such as those found in Sambrook, et al. (MolecularCloning: A Laboratory Manual. 2^(nd) , ed., Cold Spring HarborLaboratory, Cold Spring Harbor Laboratory Press, Cold Spring Harbor,N.Y., 1989).

Host cells can contain more than one vector. Thus, different nucleotidesequences can be introduced on different vectors of the same cell.Similarly, the receptor polynucleotides can be introduced either aloneor with other polynucleotides that are not related to the receptorpolynucleotides such as those providing trans-acting factors forexpression vectors. When more than one vector is introduced into a cell,the vectors can be introduced independently, co-introduced or joined tothe receptor polynucleotide vector.

In the case of bacteriophage and viral vectors, these can be introducedinto cells as packaged or encapsulated virus by standard procedures forinfection and transduction. Viral vectors can be replication-competentor replication-defective. In the case in which viral replication isdefective, replication will occur in host cells providing functions thatcomplement the defects.

Vectors generally include selectable markers that enable the selectionof the subpopulation of cells that contain the recombinant vectorconstructs. The marker can be contained in the same vector that containsthe polynucleotides described herein or may be on a separate vector.Markers include tetracycline or ampicillin-resistance genes forprokaryotic host cells and dihydrofolate reductase or neomycinresistance for eukaryotic host cells. However, any marker that providesselection for a phenotypic trait will be effective.

While the mature proteins can be produced in bacteria, yeast, mammaliancells, and other cells under the control of the appropriate regulatorysequences, cell-free transcription and translation systems can also beused to produce these proteins using RNA derived from the DNA constructsdescribed herein.

Where secretion of the polypeptide is desired, appropriate secretionsignals are incorporated into the vector. The signal sequence can beendogenous to the receptor polypeptides or heterologous to thesepolypeptides.

Where the polypeptide is not secreted into the medium, the protein canbe isolated from the host cell by standard disruption procedures,including freeze thaw, sonication, mechanical disruption, use of lysingagents and the like. The polypeptide can then be recovered and purifiedby well-known purification methods including ammonium sulfateprecipitation, acid extraction, anion or cationic exchangechromatography, phosphocellulose chromatography, hydrophobic-interactionchromatography, affinity chromatography, hydroxylapatite chromatography,lectin chromatography, or high performance liquid chromatography.

It is also understood that depending upon the host cell in recombinantproduction of the polypeptides described herein, the polypeptides canhave various glycosylation patterns, depending upon the cell, or maybenon-glycosylated as when produced in bacteria. In addition, thepolypeptides may include an initial modified methionine in some cases asa result of a host-mediated process.

Uses of Vectors and Host Cells

Specific Uses in Cardiovascular Disease

Host cells expressing the nucleic acids and polypeptides describedherein, particularly recombinant host cells, have a variety of uses inthe context of cardiovascular disease. Vectors and host cells providecellular test systems for ascertaining the effect of a given mutation onthe cellular phenotype. A desired mutant is introduced into a given hostcell and assays are performed for cellular changes includingbiochemical, morphological, functional, gene expression, and the like.In another embodiment, a desired mutant is introduced into a given hostcell and the function of a mutation can be assayed. In anotherembodiment, a desired mutant is introduced into a desired host cell anda compound is tested for its effect on gene expression, cellularchanges, and the like. In a further embodiment, a desired mutant isintroduced into a cell ex vivo so that the cell can be introduced backinto its host, such as a transgenic animal or affected individual. In afurther embodiment, a desired mutant is introduced into a host cell toprepare a transgenic host. Accordingly, preferred cells are derived fromsubjects with congestive heart failure or the risk of developing thedisorder, or from tissues known to be involved in cardiovasculardisease. Cells include, but are not limited to, cardiac myocytes, andespecially hypertrophic cardiac myocytes, as well as other cells of theheart and associated vessels. It is further understood that the generaluses of vectors and host cells described below also apply within thecontext of cardiovascular disease to cell types relevant to this type ofdisorder.

General Uses of Vectors and Host Cells

The host cells expressing the polypeptides described herein, andparticularly recombinant host cells, have a variety of uses. First, thecells are useful for producing receptor proteins or polypeptides thatcan be further purified to produce desired amounts of receptor proteinor fragments. Thus, host cells containing expression vectors are usefulfor polypeptide production.

Host cells are also useful for conducting cell-based assays involvingthe receptor or receptor fragments. Thus, a recombinant host cellexpressing a native receptor is useful to assay for compounds thatstimulate or inhibit receptor function. This includes ligand binding,gene expression at the level of transcription or translation, G-proteininteraction, and components of the signal transduction pathway.

Host cells are also useful for identifying receptor mutants in whichthese functions are affected. If the mutants naturally occur and giverise to a pathology, host cells containing the mutations are useful toassay compounds that have a desired effect on the mutant receptor (forexample, stimulating or inhibiting function) which may not be indicatedby their effect on the native receptor.

Recombinant host cells are also useful for expressing the chimericpolypeptides described herein to assess compounds that activate orsuppress activation by means of a heterologous amino terminalextracellular domain (or other binding region). Alternatively, aheterologous region spanning the entire transmembrane domain (or partsthereof) can be used to assess the effect of a desired amino terminalextracellular domain (or other binding region) on any given host cell.In this embodiment, a region spanning the entire transmembrane domain(or parts thereof) compatible with the specific host cell is used tomake the chimeric vector. Alternatively, a heterologous carboxy terminalintracellular, e.g., signal transduction, domain can be introduced intothe host cell.

Further, mutant receptors can be designed in which one or more of thevarious functions is engineered to be increased or decreased (e.g.,ligand binding or G-protein binding) and used to augment or replacereceptor proteins in an individual. Thus, host cells can provide atherapeutic benefit by replacing an aberrant receptor or providing anaberrant receptor that provides a therapeutic result. In one embodiment,the cells provide receptors that are abnormally active.

In another embodiment, the cells provide receptors that are abnormallyinactive. These receptors can compete with endogenous receptors in theindividual.

In another embodiment, cells expressing receptors that cannot beactivated, are introduced into an individual in order to compete withendogenous receptors for ligand. For example, in the case in whichexcessive ligand is part of a treatment modality, it may be necessary toinactivate this ligand at a specific point in treatment. Providing cellsthat compete for the ligand, but which cannot be affected by receptoractivation would be beneficial.

Homologously recombinant host cells can also be produced that allow thein situ alteration of endogenous receptor polynucleotide sequences in ahost cell genome. This technology is more fully described in WO93/09222, WO 91/12650 and U.S. Pat. No. 5,641,670. Briefly, specificpolynucleotide sequences corresponding to the receptor polynucleotidesor sequences proximal or distal to a receptor gene are allowed tointegrate into a host cell genome by homologous recombination whereexpression of the gene can be affected. In one embodiment, regulatorysequences are introduced that either increase or decrease expression ofan endogenous sequence. Accordingly, a receptor protein can be producedin a cell not normally producing it, or increased expression of receptorprotein can result in a cell normally producing the protein at aspecific level. Alternatively, the entire gene can be deleted. Stillfurther, specific mutations can be introduced into any desired region ofthe gene to produce mutant receptor proteins. Such mutations could beintroduced, for example, into the specific functional regions such asthe ligand-binding site or the G-protein binding site.

In one embodiment, the host cell can be a fertilized oocyte or embryonicstem cell that can be used to produce a transgenic animal containing thealtered receptor gene. Alternatively, the host cell can be a stem cellor other early tissue precursor that gives rise to a specific subset ofcells and can be used to produce transgenic tissues in an animal. Seealso Thomas et al., Cell 51:503 (1987) for a description of homologousrecombination vectors. The vector is introduced into an embryonic stemcell line (e.g., by electroporation) and cells in which the introducedgene has homologously recombined with the endogenous receptor gene isselected (see e.g., Li, E. et al., Cell 69:915 (1992). The selectedcells are then injected into a blastocyst of an animal (e.g., a mouse)to form aggregation chimeras (see e.g., Bradley, A. in Teratocarcinomasand Embryonic Stem Cells: A Practical Approach, E. J. Robertson, ed.(IRL, Oxford, 1987) pp. 113-152). A chimeric embryo can then beimplanted into a suitable pseudopregnant female foster animal and theembryo brought to term. Progeny harboring the homologously recombinedDNA in their germ cells can be used to breed animals in which all cellsof the animal contain the homologously recombined DNA by germlinetransmission of the transgene. Methods for constructing homologousrecombination vectors and homologous recombinant animals are describedfurther in Bradley, A. (1991) Current Opinion in Biotechnology 2:823-829and in PCT International Publication Nos. WO 90/11354; WO 91/01140; andWO 93/04169.

The genetically engineered host cells can be used to produce non-humantransgenic animals. A transgenic animal is preferably a mammal, forexample a rodent, such as a rat or mouse, in which one or more of thecells of the animal include a transgene. A transgene is exogenous DNAwhich is integrated into the genome of a cell from which a transgenicanimal develops and which remains in the genome of the mature animal inone or more cell types or tissues of the transgenic animal. Theseanimals are useful for studying the function of a receptor protein andidentifying and evaluating modulators of receptor protein activity.

Other examples of transgenic animals include non-human primates, sheep,dogs, cows, goats, chickens, and amphibians.

In one embodiment, a host cell is a fertilized oocyte or an embryonicstem cell into which receptor polynucleotide sequences have beenintroduced.

A transgenic animal can be produced by introducing nucleic acid into themale pronuclei of a fertilized oocyte, e.g., by microinjection,retroviral infection, and allowing the oocyte to develop in apseudopregnant female foster animal. Any of the receptor nucleotidesequences can be introduced as a transgene into the genome of anon-human animal, such as a mouse.

Any of the regulatory or other sequences useful in expression vectorscan form part of the transgenic sequence. This includes intronicsequences and polyadenylation signals, if not already included. Atissue-specific regulatory sequence(s) can be operably linked to thetransgene to direct expression of the receptor protein to particularcells.

Methods for generating transgenic animals via embryo manipulation andmicroinjection, particularly animals such as mice, have becomeconventional in the art and are described, for example, in U.S. Pat.Nos. 4,736,866 and 4,870,009, both by Leder et al., U.S. Pat. No.4,873,191 by Wagner et al. and in Hogan, B., Manipulating the MouseEmbryo, (Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.,1986). Similar methods are used for production of other transgenicanimals. A transgenic founder animal can be identified based upon thepresence of the transgene in its genome and/or expression of transgenicmRNA in tissues or cells of the animals. A transgenic founder animal canthen be used to breed additional animals carrying the transgene.Moreover, transgenic animals carrying a transgene can further be bred toother transgenic animals carrying other transgenes. A transgenic animalalso includes animals in which the entire animal or tissues in theanimal have been produced using the homologously recombinant host cellsdescribed herein.

In another embodiment, transgenic non-human animals can be producedwhich contain selected systems which allow for regulated expression ofthe transgene. One example of such a system is the cre/loxP recombinasesystem of bacteriophage P1. For a description of the cre/loxPrecombinase system, see, e.g., Lakso et al. PNAS 89:6232-6236 (1992).Another example of a recombinase system is the FLP recombinase system ofS. cerevisiae (O'Gorman et al. Science 251:1351-1355 (1991). If acre/loxP recombinase system is used to regulate expression of thetransgene, animals containing transgenes encoding both the Crerecombinase and a selected protein is required. Such animals can beprovided through the construction of “double” transgenic animals, e.g.,by mating two transgenic animals, one containing a transgene encoding aselected protein and the other containing a transgene encoding arecombinase.

Clones of the non-human transgenic animals described herein can also beproduced according to the methods described in Wilmut, I. et al. Nature385:810-813 (1997) and PCT International Publication Nos. WO 97/07668and WO 97/07669. In brief, a cell, e.g., a somatic cell, from thetransgenic animal can be isolated and induced to exit the growth cycleand enter G_(o) phase. The quiescent cell can then be fused, e.g.,through the use of electrical pulses, to an enucleated oocyte from ananimal of the same species from which the quiescent cell is isolated.The reconstructed oocyte is then cultured such that it develops tomorula or blastocyst and then transferred to a pseudopregnant femalefoster animal. The offspring born of this female foster animal will be aclone of the animal from which the cell, e.g., the somatic cell, isisolated.

Transgenic animals containing recombinant cells that express thepolypeptides described herein are useful to conduct the assays describedherein in an in vivo context. Accordingly, the various physiologicalfactors that are present in vivo and that could effect ligand binding,receptor activation, and signal transduction, may not be evident from invitro cell-free or cell-based assays. Accordingly, it is useful toprovide non-human transgenic animals to assay in vivo receptor function,including ligand interaction, the effect of specific mutant receptors onreceptor function and ligand interaction, and the effect of chimericreceptors. It is also possible to assess the effect of null mutations,that is mutations that substantially or completely eliminate one or morereceptor functions.

Pharmaceutical Compositions

The receptor nucleic acid molecules, protein (particularly fragmentssuch as the amino terminal extracellular domain), modulators of theprotein, and antibodies (also referred to herein as “active compounds”)can be incorporated into pharmaceutical compositions suitable foradministration to a subject, e.g., a human. Such compositions typicallycomprise the nucleic acid molecule, protein, modulator, or antibody anda pharmaceutically acceptable carrier.

As used herein the language “pharmaceutically acceptable carrier” isintended to include any and all solvents, dispersion media, coatings,antibacterial and antifungal agents, isotonic and absorption delayingagents, and the like, compatible with pharmaceutical administration. Theuse of such media and agents for pharmaceutically active substances iswell known in the art. Except insofar as any conventional media or agentis incompatible with the active compound, such media can be used in thecompositions of the invention. Supplementary active compounds can alsobe incorporated into the compositions. A pharmaceutical composition ofthe invention is formulated to be compatible with its intended route ofadministration. Examples of routes of administration include parenteral,e.g., intravenous, intradermal, subcutaneous, oral (e.g., inhalation),transdermal (topical), transmucosal, and rectal administration.Solutions or suspensions used for parenteral, intradermal, orsubcutaneous application can include the following components: a sterilediluent such as water for injection, saline solution, fixed oils,polyethylene glycols, glycerine, propylene glycol or other syntheticsolvents; antibacterial agents such as benzyl alcohol or methylparabens; antioxidants such as ascorbic acid or sodium bisulfite;chelating agents such as ethylenediaminetetraacetic acid; buffers suchas acetates, citrates or phosphates and agents for the adjustment oftonicity such as sodium chloride or dextrose. pH can be adjusted withacids or bases, such as hydrochloric acid or sodium hydroxide. Theparenteral preparation can be enclosed in ampules, disposable syringesor multiple dose vials made of glass or plastic.

Pharmaceutical compositions suitable for injectable use include sterileaqueous solutions (where water soluble) or dispersions and sterilepowders for the extemporaneous preparation of sterile injectablesolutions or dispersion. For intravenous administration, suitablecarriers include physiological saline, bacteriostatic water, CremophorEL™ (BASF, Parsippany, N.J.) or phosphate buffered saline (PBS). In allcases, the composition must be sterile and should be fluid to the extentthat easy syringability exists. It must be stable under the conditionsof manufacture and storage and must be preserved against thecontaminating action of microorganisms such as bacteria and fungi. Thecarrier can be a solvent or dispersion medium containing, for example,water, ethanol, polyol (for example, glycerol, propylene glycol, andliquid polyethylene glycol, and the like), and suitable mixturesthereof. The proper fluidity can be maintained, for example, by the useof a coating such as lecithin, by the maintenance of the requiredparticle size in the case of dispersion and by the use of surfactants.Prevention of the action of microorganisms can be achieved by variousantibacterial and antifungal agents, for example, parabens,chlorobutanol, phenol, ascorbic acid, thimerosal, and the like. In manycases, it will be preferable to include isotonic agents, for example,sugars, polyalcohols such as manitol, sorbitol, sodium chloride in thecomposition. Prolonged absorption of the injectable compositions can bebrought about by including in the composition an agent which delaysabsorption, for example, aluminum monostearate and gelatin.

Sterile injectable solutions can be prepared by incorporating the activecompound (e.g., a receptor protein or anti-receptor antibody) in therequired amount in an appropriate solvent with one or a combination ofingredients enumerated above, as required, followed by filteredsterilization. Generally, dispersions are prepared by incorporating theactive compound into a sterile vehicle which contains a basic dispersionmedium and the required other ingredients from those enumerated above.In the case of sterile powders for the preparation of sterile injectablesolutions, the preferred methods of preparation are vacuum drying andfreeze-drying which yields a powder of the active ingredient plus anyadditional desired ingredient from a previously sterile-filteredsolution thereof.

Oral compositions generally include an inert diluent or an ediblecarrier. They can be enclosed in gelatin capsules or compressed intotablets. For oral administration, the agent can be contained in entericforms to survive the stomach or further coated or mixed to be releasedin a particular region of the GI tract by known methods. For the purposeof oral therapeutic administration, the active compound can beincorporated with excipients and used in the form of tablets, troches,or capsules. Oral compositions can also be prepared using a fluidcarrier for use as a mouthwash, wherein the compound in the fluidcarrier is applied orally and swished and expectorated or swallowed.Pharmaceutically compatible binding agents, and/or adjuvant materialscan be included as part of the composition. The tablets, pills,capsules, troches and the like can contain any of the followingingredients, or compounds of a similar nature: a binder such asmicrocrystalline cellulose, gum tragacanth or gelatin; an excipient suchas starch or lactose, a disintegrating agent such as alginic acid,Primogel, or corn starch; a lubricant such as magnesium stearate orSterotes; a glidant such as colloidal silicon dioxide; a sweeteningagent such as sucrose or saccharin; or a flavoring agent such aspeppermint, methyl salicylate, or orange flavoring.

For administration by inhalation, the compounds are delivered in theform of an aerosol spray from pressured container or dispenser whichcontains a suitable propellant, e.g., a gas such as carbon dioxide, or anebulizer.

Systemic administration can also be by transmucosal or transdermalmeans. For transmucosal or transdermal administration, penetrantsappropriate to the barrier to be permeated are used in the formulation.Such penetrants are generally known in the art, and include, forexample, for transmucosal administration, detergents, bile salts, andfusidic acid derivatives. Transmucosal administration can beaccomplished through the use of nasal sprays or suppositories. Fortransdermal administration, the active compounds are formulated intoointments, salves, gels, or creams as generally known in the art.

The compounds can also be prepared in the form of suppositories (e.g.,with conventional suppository bases such as cocoa butter and otherglycerides) or retention enemas for rectal delivery.

In one embodiment, the active compounds are prepared with carriers thatwill protect the compound against rapid elimination from the body, suchas a controlled release formulation, including implants andmicroencapsulated delivery systems. Biodegradable, biocompatiblepolymers can be used, such as ethylene vinyl acetate, polyanhydrides,polyglycolic acid, collagen, polyorthoesters, and polylactic acid.Methods for preparation of such formulations will be apparent to thoseskilled in the art. The materials can also be obtained commercially fromAlza Corporation and Nova Pharmaceuticals, Inc. Liposomal suspensions(including liposomes targeted to infected cells with monoclonalantibodies to viral antigens) can also be used as pharmaceuticallyacceptable carriers. These can be prepared according to methods known tothose skilled in the art, for example, as described in U.S. Pat. No.4,522,811.

It is especially advantageous to formulate oral or parenteralcompositions in dosage unit form for ease of administration anduniformity of dosage. “Dosage unit form” as used herein refers tophysically discrete units suited as unitary dosages for the subject tobe treated; each unit containing a predetermined quantity of activecompound calculated to produce the desired therapeutic effect inassociation with the required pharmaceutical carrier. The specificationfor the dosage unit forms of the invention are dictated by and directlydependent on the unique characteristics of the active compound and theparticular therapeutic effect to be achieved, and the limitationsinherent in the art of compounding such an active compound for thetreatment of individuals.

The nucleic acid molecules of the invention can be inserted into vectorsand used as gene therapy vectors. Gene therapy vectors can be deliveredto a subject by, for example, intravenous injection, localadministration (U.S. Pat. No. 5,328,470) or by stereotactic injection(see e.g., Chen et al., PNAS 91:3054-3057 (1994)). The pharmaceuticalpreparation of the gene therapy vector can include the gene therapyvector in an acceptable diluent, or can comprise a slow release matrixin which the gene delivery vehicle is imbedded. Alternatively, where thecomplete gene delivery vector can be produced intact from recombinantcells, e.g. retroviral vectors, the pharmaceutical preparation caninclude one or more cells which produce the gene delivery system.

The pharmaceutical compositions can be included in a container, pack, ordispenser together with instructions for administration.

This invention may be embodied in many different forms and should not beconstrued as limited to the embodiments set forth herein; rather, theseembodiments are provided so that this disclosure will fully convey theinvention to those skilled in the art. Many modifications and otherembodiments of the invention will come to mind in one skilled in the artto which this invention pertains having the benefit of the teachingspresented in the foregoing description. Although specific terms areemployed, they are used as in the art unless otherwise indicated.

EXAMPLE I

To further explore the function of the novel G-protein coupled receptorin cardiac hypertrophy, several independent sets of transgenic mice weremade in which the receptor could be specifically overexpressed incardiomyocytes. Expression constructs included the alpha-MHC promoteroperably linked to the receptor coding sequence. This cardiomyocytespecific promoter is well-characterized in the art. Constructs were alsodesigned in which a CMV promoter was operably linked to the receptorcoding sequence. The results of these experiments show that transgenicmice specifically overexpressing the novel receptor gene developcardiomyocyte hypertrophy. Many of these died from heart failure.

An antibody directed against a C-terminal peptide (SEQ ID NO:12,corresponds to amino acids 348-361 of SEQ ID NO:1 ), DTSVKRNDLSIISG, wasused to detect receptor expression in wild type and transgenic (F1)mice. Protein was extracted from hearts of control and transgenicanimals. The result showed that the C-terminal antibody could identifythe protein in a heart protein extract from transgenic mice in which thereceptor gene is expressed from the alpha-MHC promoter. In contrast, nosignal was detected in non-transgenic control animals.

A heart-body weight ratio was assessed in animals affected byoverexpression of the receptor gene product. The ratio was significantlyhigher in a significant number of affected mice. The ratios ranged fromapproximately 1.5 to approximately 2.7. It was also noted that in theaffected mice, overexpression of the gene detrimentally affectedalertness. Further, pathology results showed an enlargement of theatrium as well as ventricle thrombosis in the atrium. In addition, edemain the chest and breathing difficulties were observed.

Histopathology of the hearts from affected animals showed biventriculardilatation, cardiomyocyte hypertrophy, atrial thrombi, and interstitialfibrosis.

EXAMPLE II

The 14273 receptor was shown to be upregulated in a rat pressureoverload model, as seen by in situ hybridization. The model wasgenerated by placing a constrictive band around the aorta to induce astate of cardiac hypertrophy. The receptor was shown to be induced atthe RNA level by 22 weeks following banding of the aorta. This increasein expression was correlated with the hypertrophic phenotype.Independent results were obtained with two independent mouse probes.Accordingly, the expression of the receptor is induced in the failedheart, collected 22 weeks after aortic banding, using a non-bandedcontrol heart as a comparison.

Sections (10 μm for embryos and 8 μm for organ sections) were postfixedwith 4% formaldehyde in DEPC-treated 1× phosphate-buffered saline atroom temperature for 10 minutes before being rinsed twice inDEPC-treated 1× phosphate-buffered saline and once in 0.1 Mtriethanolamine-HCl (pH 8.0). Following incubation in 0.25% aceticanhydride-0.1 M triethanolamine-HCl for 10 minutes, sections were rinsedin DEPC-treated 2×SSC (1×SSC is 0.15M NaCl plus 0.015M sodium citrate).Tissue was dehydrated through a series of ethanol washes, incubated in100% chloroform for 5 minutes, and then rinsed in 100% ethanol for 1minute and 95% ethanol for 1 minute and allowed to air dry.

The hybridization was performed using a ³⁵S-radiolabeled cRNA probe.

The sequence of two mouse probes used for in situ hybridization of14273:

TGTGGAGTCCCATCATCATCACCATCCTCCTCATCTTGATCCAAAACTTCCGGCAGGACCTGGTCATCTGGCCATCCCTTTTCTTCTGGGTGGTGGCCTTCACGTTTGCCAACTCTGCCCTAAACCCCATACTGTACAACATGTCGCTGTTCAGGAACGAATGGAGGAAGATTTTTTGCTG (SEQ ID NO:14, corresponds tonucleotides 1021-1201 of SEQ ID NO: 5)AAGAGGCTTACGCTGAGCTTGGCATACTCTGAGAGCCACCAGATCCGAGTGTCCCAACAAGACTACCGACTCTTCCGCACGCTCTTCCTGCTCATGGTTTCCTTCTTCATCATGTGGAGTCCCATCATCATCACCATC (SEQ ID NO: 15, corresponds tonucleotides 909-1036 of SEQ ID NO:5)

?!

EXAMPLE III

Transgenic mice expressing the 14273 receptor were shown to developheart failure. Receptor mRNA and protein levels were correlated with theseverity of the phenotype. The sequence of events were: hypertrophy(both nuclear and cytoplasmic) of cardiomyocytes, development ofeosinophilic nuclei (a hallmark of hypertrophy), myocytedisorganization, atrial and ventricular loss of myocytes, interstitialfibrosis, fibroelastosis, and thrombosis. Four transgenic lines showedsevere symptoms, with pathology or death in every member studied,generally in weeks. In this group, relatively high RNA and proteinexpression was observed.

In a second group, pathology or death was observed, but not in all ofthe animals, in a space of weeks to around three months. In this group,expression levels of the receptor were lower than those with the firstgroup, which had the most severe symptoms.

In the third group, the transgenic mice showed no detectable symptoms.However, the histological results showed cardiohypertrophy with variousdegrees at the age of two to four months. The expression levels of thereceptor in this group were the lowest among the three groups oftransgenic mice.

In Northern blots developed against tissues from each of these groups,high expression of the receptor was observed compared to a wild-typecontrol. In each of these samples, the expression of atrial natriureticfactor, ANF, was also shown to be increased, relative to expression inwild-type controls.

1. A method for identifying a compound which binds to a polypeptideselected from the group consisting of: (a) an isolated polypeptidecomprising the amino acid sequence shown in SEQ ID NO:1; (b) an isolatedpolypeptide comprising the amino acid sequence encoded by the nucleotidesequence of SEQ ID NO:2; and (c) an isolated polypeptide comprising anamino acid sequence that is at least 95% identical to the amino acidsequence shown in SEQ ID NO:1, the method comprising: i) contacting thepolypeptide, or a cell expressing the polypeptide with a test compoundunder conditions that allow the compound to bind the polypeptide, ii)detecting the binding of the test compound to the polypeptide, therebyidentifying a compound which binds the polypeptide.
 2. The method ofclaim 1, wherein the binding of the test compound to the polypeptide isdetected by a method selected from the group consisting of: a) directdetection of test compound/polypeptide binding; b) a competition bindingassay; and c) an immunoassay.
 3. The method of claim 1, wherein the testcompound is selected from the group consisting of a peptide,phosphopeptide, antibody, and a small molecule.
 4. The method of claim1, wherein the test compound is labeled.